Additional "Add More Additions" button causes "File Download" dialogue box in Internet Explorer!

I've searched but can't find anyone else reporting this issue, which seems to be Internet Explorer-specific.

As you can see from the attached screen shot, using IE 8, when you create a new Date Event, if you choose Repeat > Additional > Add More Additions, instead of simply generating an additional date field to enter a 3rd date for the event, IE instead generates a "File Download - Security Warning" dialogue box which tries to download the "file", which is named "field_dateXXXXXXX" (with a randomly-generated string of letters/numbers after it).

When I save the file and open it using NotePad, it displays the following code (see below), which I presume is simply the script that the Add More Additions button is supposed to run.

Any suggestions? I've tried tinkering with the IE security settings, but it seems to be inherent. This is a major issue for my client, who is unlikely to be willing to switch from IE to Firefox/Chrome/etc (she's rather stubborn about these sorts of things).

Here's the code that the downloaded file contains:

{ "status": true, "data": "\x3cdiv id=\"date-repeat-additions\" class=\"date-repeat\"\x3e\x3cfieldset class=\" collapsible collapsed\"\x3e\x3clegend\x3eAdditional\x3c/legend\x3e\x3cdiv class=\"description\"\x3eDates to add to the list of repeating dates.\x3c/div\x3e\x3cdiv class=\"container-inline-date form-item date-clear-block\"\x3e\x3cdiv class=\"form-item\" id=\"edit-field-date-rrule-additions-RDATE-0-datetime-wrapper\"\x3e\n \x3cdiv class=\"form-item\" id=\"edit-field-date-rrule-additions-RDATE-0-datetime-datepicker-popup-0-wrapper\"\x3e\n \x3cinput type=\"text\" maxlength=\"30\" name=\"field_date[rrule][additions][RDATE][0][datetime][date]\" id=\"edit-field-date-rrule-additions-RDATE-0-datetime-datepicker-popup-0\" size=\"20\" value=\"\" class=\"form-text\" /\x3e\n \x3cdiv class=\"description\"\x3e Format: 11/15/2012\x3c/div\x3e\n\x3c/div\x3e\n\n\x3c/div\x3e\n\x3c/div\x3e\x3cinput type=\"hidden\" name=\"field_date[rrule][additions][RDATE][0][tz]\" id=\"edit-field-date-rrule-additions-RDATE-0-tz\" value=\"America/Detroit\" /\x3e\n\x3cinput type=\"hidden\" name=\"field_date[rrule][additions][RDATE][0][all_day]\" id=\"edit-field-date-rrule-additions-RDATE-0-all-day\" value=\"1\" /\x3e\n\x3cinput type=\"hidden\" name=\"field_date[rrule][additions][RDATE][0][granularity]\" id=\"edit-field-date-rrule-additions-RDATE-0-granularity\" value=\"a:3:{i:0;s:4:\x26quot;year\x26quot;;i:1;s:5:\x26quot;month\x26quot;;i:2;s:3:\x26quot;day\x26quot;;}\" /\x3e\n\x3cinput type=\"submit\" name=\"op\" id=\"edit-field-date-rrule-additions-additions-addmore\" value=\"Add more additions\" class=\"form-submit\" /\x3e\n\x3c/fieldset\x3e\n\x3c/div\x3e\x3cscript type=\"text/javascript\"\x3ejQuery.extend(Drupal.settings, { \"basePath\": \"/\", \"admin_menu\": { \"margin_top\": 1, \"position_fixed\": 1 }, \"nice_menus_options\": { \"delay\": \"800\", \"speed\": \"fast\" }, \"cron\": { \"basePath\": \"/poormanscron\", \"runNext\": 1353039546 }, \"extlink\": { \"extTarget\": \"_blank\", \"extClass\": 0, \"extSubdomains\": 1, \"extExclude\": \"\", \"extInclude\": \".*doc$|.*pdf$\", \"extAlert\": 0, \"extAlertText\": \"This link will take you to an external web site. We are not responsible for their content.\", \"mailtoClass\": 0 }, \"ckeditor\": { \"module_path\": \"/sites/all/modules/ckeditor\", \"editor_path\": \"/sites/all/modules/ckeditor/ckeditor\", \"ajaxToken\": \"5070a7fe9baff937cdf6189ecb9e3226\", \"query\": \"date_repeat_get_exception_form_ajax/additions/field_date\", \"default_input_format\": \"2\", \"theme\": \"cti_flex\", \"settings\": { \"edit-body\": { \"customConfig\": \"/sites/all/modules/ckeditor/ckeditor.config.js?1334366655\", \"defaultLanguage\": \"en\", \"toolbar\": \"[\\r\\n [\\\'Source\\\'],\\r\\n [\\\'Cut\\\',\\\'Copy\\\',\\\'Paste\\\',\\\'PasteText\\\',\\\'PasteFromWord\\\',\\\'-\\\',\\\'SpellChecker\\\',\\\'Scayt\\\'],\\r\\n [\\\'Undo\\\',\\\'Redo\\\',\\\'Find\\\',\\\'Replace\\\',\\\'-\\\',\\\'SelectAll\\\',\\\'RemoveFormat\\\'],\\r\\n [\\\'Image\\\',\\\'Flash\\\',\\\'Table\\\',\\\'HorizontalRule\\\',\\\'Smiley\\\',\\\'SpecialChar\\\',\\\'Iframe\\\'],\\r\\n \\\'/\\\',\\r\\n [\\\'Bold\\\',\\\'Italic\\\',\\\'Underline\\\',\\\'Strike\\\',\\\'-\\\',\\\'Subscript\\\',\\\'Superscript\\\'],\\r\\n [\\\'NumberedList\\\',\\\'BulletedList\\\',\\\'-\\\',\\\'Outdent\\\',\\\'Indent\\\',\\\'Blockquote\\\',\\\'CreateDiv\\\'],\\r\\n [\\\'JustifyLeft\\\',\\\'JustifyCenter\\\',\\\'JustifyRight\\\',\\\'JustifyBlock\\\',\\\'-\\\',\\\'BidiRtl\\\',\\\'BidiLtr\\\'],\\r\\n [\\\'Link\\\',\\\'Unlink\\\',\\\'Anchor\\\'],\\r\\n \\\'/\\\',\\r\\n [\\\'Format\\\',\\\'Font\\\',\\\'FontSize\\\'],\\r\\n [\\\'TextColor\\\',\\\'BGColor\\\'],\\r\\n [\\\'Maximize\\\',\\\'ShowBlocks\\\'],\\r\\n [\\\'DrupalBreak\\\',\\\'IMCE\\\',\\\'MediaEmbed\\\']\\r\\n]\", \"enterMode\": 1, \"shiftEnterMode\": 2, \"toolbarStartupExpanded\": true, \"width\": \"100%\", \"height\": 420, \"skin\": \"kama\", \"format_tags\": \"p;div;pre;address;h1;h2;h3;h4;h5;h6\", \"loadPlugins\": { \"counter\": { \"name\": \"counter\", \"desc\": \"Plugin to count symbols, symbols without blanks and words\", \"path\": \"/sites/all/modules/ckeditor/plugins/counter/\", \"buttons\": false, \"default\": \"f\" }, \"drupalbreaks\": { \"name\": \"drupalbreaks\", \"desc\": \"Plugin for inserting Drupal teaser and page breaks.\", \"path\": \"/sites/all/modules/ckeditor/plugins/drupalbreaks/\", \"buttons\": { \"DrupalBreak\": { \"label\": \"DrupalBreak\", \"icon\": \"images/drupalbreak.png\" } }, \"default\": \"t\" }, \"imce\": { \"name\": \"imce\", \"desc\": \"Plugin for inserting files from imce without image dialog\", \"path\": \"/sites/all/modules/ckeditor/plugins/imce/\", \"buttons\": { \"IMCE\": { \"label\": \"IMCE\", \"icon\": \"images/icon.png\" } }, \"default\": \"f\" }, \"mediaembed\": { \"name\": \"mediaembed\", \"desc\": \"Plugin for inserting Drupal embeded media\", \"path\": \"/sites/all/modules/ckeditor/plugins/mediaembed/\", \"buttons\": { \"MediaEmbed\": { \"label\": \"MediaEmbed\", \"icon\": \"images/icon.png\" } }, \"default\": \"f\" }, \"tableresize\": { \"name\": \"tableresize\", \"desc\": \"Table Resize plugin\", \"path\": \"/sites/all/modules/ckeditor/ckeditor/plugins/tableresize/\", \"buttons\": false, \"default\": \"t\" } }, \"scayt_autoStartup\": false, \"scayt_sLang\": \"en_US\", \"forcePasteAsPlainText\": true, \"filebrowserBrowseUrl\": \"/index.php?q=imce\\x26app=ckeditor|sendto@ckeditor_fileUrl|\", \"stylesCombo_stylesSet\": \"drupal:/sites/all/modules/ckeditor/ckeditor.styles.js\", \"contentsCss\": [ \"/sites/all/modules/ckeditor/ckeditor.css?2\", \"/sites/all/modules/ckeditor/ckeditor/contents.css?2\" ], \"input_format\": \"2\" } }, \"autostart\": { \"edit-body\": true } }, \"ahah\": { \"edit-attach\": { \"url\": \"/upload/js\", \"event\": \"mousedown\", \"keypress\": true, \"wrapper\": \"attach-wrapper\", \"selector\": \"#edit-attach\", \"effect\": \"none\", \"method\": \"replace\", \"progress\": { \"type\": \"bar\", \"message\": \"Please wait...\" }, \"button\": { \"attach\": \"Attach\" } }, \"edit-field-date-rrule-exceptions-exceptions-addmore\": { \"url\": \"/date_repeat_get_exception_form_ajax/exceptions/field_date\", \"event\": \"click\", \"keypress\": null, \"wrapper\": \"date-repeat-exceptions\", \"selector\": \"#edit-field-date-rrule-exceptions-exceptions-addmore\", \"effect\": \"fade\", \"method\": \"replace\", \"progress\": { \"type\": \"throbber\" }, \"button\": { \"op\": \"Add more exceptions\" } }, \"edit-field-date-rrule-additions-additions-addmore\": { \"url\": \"/date_repeat_get_exception_form_ajax/additions/field_date\", \"event\": \"click\", \"keypress\": null, \"wrapper\": \"date-repeat-additions\", \"selector\": \"#edit-field-date-rrule-additions-additions-addmore\", \"effect\": \"fade\", \"method\": \"replace\", \"progress\": { \"type\": \"throbber\" }, \"button\": { \"op\": \"Add more additions\" } } }, \"datePopup\": { \"edit-field-date-rrule-UNTIL-datetime-datepicker-popup-0\": { \"func\": \"datepicker\", \"settings\": { \"prevText\": \"\\x26laquo;\", \"nextText\": \"\\x26raquo;\", \"currentText\": \"Today\", \"changeMonth\": true, \"changeYear\": true, \"clearText\": \"Clear\", \"closeText\": \"Close\", \"firstDay\": 0, \"dayNames\": [ \"Sunday\", \"Monday\", \"Tuesday\", \"Wednesday\", \"Thursday\", \"Friday\", \"Saturday\" ], \"dayNamesShort\": [ \"Sun\", \"Mon\", \"Tue\", \"Wed\", \"Thu\", \"Fri\", \"Sat\" ], \"dayNamesMin\": [ \"SU\", \"MO\", \"TU\", \"WE\", \"TH\", \"FR\", \"SA\" ], \"monthNames\": [ \"January\", \"February\", \"March\", \"April\", \"May\", \"June\", \"July\", \"August\", \"September\", \"October\", \"November\", \"December\" ], \"monthNamesShort\": [ \"Jan\", \"Feb\", \"Mar\", \"Apr\", \"May\", \"Jun\", \"Jul\", \"Aug\", \"Sep\", \"Oct\", \"Nov\", \"Dec\" ], \"autoPopUp\": \"focus\", \"closeAtTop\": false, \"speed\": \"immediate\", \"dateFormat\": \"mm/dd/yy\", \"yearRange\": \"+0:+20\", \"fromTo\": false, \"defaultDate\": \"0y\" } }, \"edit-field-date-rrule-exceptions-EXDATE-0-datetime-datepicker-popup-0\": { \"func\": \"datepicker\", \"settings\": { \"prevText\": \"\\x26laquo;\", \"nextText\": \"\\x26raquo;\", \"currentText\": \"Today\", \"changeMonth\": true, \"changeYear\": true, \"clearText\": \"Clear\", \"closeText\": \"Close\", \"firstDay\": 0, \"dayNames\": [ \"Sunday\", \"Monday\", \"Tuesday\", \"Wednesday\", \"Thursday\", \"Friday\", \"Saturday\" ], \"dayNamesShort\": [ \"Sun\", \"Mon\", \"Tue\", \"Wed\", \"Thu\", \"Fri\", \"Sat\" ], \"dayNamesMin\": [ \"SU\", \"MO\", \"TU\", \"WE\", \"TH\", \"FR\", \"SA\" ], \"monthNames\": [ \"January\", \"February\", \"March\", \"April\", \"May\", \"June\", \"July\", \"August\", \"September\", \"October\", \"November\", \"December\" ], \"monthNamesShort\": [ \"Jan\", \"Feb\", \"Mar\", \"Apr\", \"May\", \"Jun\", \"Jul\", \"Aug\", \"Sep\", \"Oct\", \"Nov\", \"Dec\" ], \"autoPopUp\": \"focus\", \"closeAtTop\": false, \"speed\": \"immediate\", \"dateFormat\": \"mm/dd/yy\", \"yearRange\": \"+0:+20\", \"fromTo\": false, \"defaultDate\": \"0y\" } }, \"edit-field-date-rrule-additions-RDATE-0-datetime-datepicker-popup-0\": { \"func\": \"datepicker\", \"settings\": { \"prevText\": \"\\x26laquo;\", \"nextText\": \"\\x26raquo;\", \"currentText\": \"Today\", \"changeMonth\": true, \"changeYear\": true, \"clearText\": \"Clear\", \"closeText\": \"Close\", \"firstDay\": 0, \"dayNames\": [ \"Sunday\", \"Monday\", \"Tuesday\", \"Wednesday\", \"Thursday\", \"Friday\", \"Saturday\" ], \"dayNamesShort\": [ \"Sun\", \"Mon\", \"Tue\", \"Wed\", \"Thu\", \"Fri\", \"Sat\" ], \"dayNamesMin\": [ \"SU\", \"MO\", \"TU\", \"WE\", \"TH\", \"FR\", \"SA\" ], \"monthNames\": [ \"January\", \"February\", \"March\", \"April\", \"May\", \"June\", \"July\", \"August\", \"September\", \"October\", \"November\", \"December\" ], \"monthNamesShort\": [ \"Jan\", \"Feb\", \"Mar\", \"Apr\", \"May\", \"Jun\", \"Jul\", \"Aug\", \"Sep\", \"Oct\", \"Nov\", \"Dec\" ], \"autoPopUp\": \"focus\", \"closeAtTop\": false, \"speed\": \"immediate\", \"dateFormat\": \"mm/dd/yy\", \"yearRange\": \"+0:+20\", \"fromTo\": false, \"defaultDate\": \"0y\" } }, \"edit-field-date-value-datepicker-popup-0\": { \"func\": \"datepicker\", \"settings\": { \"prevText\": \"\\x26laquo;\", \"nextText\": \"\\x26raquo;\", \"currentText\": \"Today\", \"changeMonth\": true, \"changeYear\": true, \"clearText\": \"Clear\", \"closeText\": \"Close\", \"firstDay\": 0, \"dayNames\": [ \"Sunday\", \"Monday\", \"Tuesday\", \"Wednesday\", \"Thursday\", \"Friday\", \"Saturday\" ], \"dayNamesShort\": [ \"Sun\", \"Mon\", \"Tue\", \"Wed\", \"Thu\", \"Fri\", \"Sat\" ], \"dayNamesMin\": [ \"SU\", \"MO\", \"TU\", \"WE\", \"TH\", \"FR\", \"SA\" ], \"monthNames\": [ \"January\", \"February\", \"March\", \"April\", \"May\", \"June\", \"July\", \"August\", \"September\", \"October\", \"November\", \"December\" ], \"monthNamesShort\": [ \"Jan\", \"Feb\", \"Mar\", \"Apr\", \"May\", \"Jun\", \"Jul\", \"Aug\", \"Sep\", \"Oct\", \"Nov\", \"Dec\" ], \"autoPopUp\": \"focus\", \"closeAtTop\": false, \"speed\": \"immediate\", \"dateFormat\": \"mm/dd/yy\", \"yearRange\": \"+0:+20\", \"fromTo\": false, \"defaultDate\": \"0y\" } }, \"edit-field-date-value-timeEntry-popup-1\": { \"func\": \"timeEntry\", \"settings\": { \"show24Hours\": false, \"showSeconds\": false, \"timeSteps\": [ 1, 15, 0 ], \"spinnerImage\": \"\", \"fromTo\": false } }, \"edit-field-date-value2-datepicker-popup-0\": { \"func\": \"datepicker\", \"settings\": { \"prevText\": \"\\x26laquo;\", \"nextText\": \"\\x26raquo;\", \"currentText\": \"Today\", \"changeMonth\": true, \"changeYear\": true, \"clearText\": \"Clear\", \"closeText\": \"Close\", \"firstDay\": 0, \"dayNames\": [ \"Sunday\", \"Monday\", \"Tuesday\", \"Wednesday\", \"Thursday\", \"Friday\", \"Saturday\" ], \"dayNamesShort\": [ \"Sun\", \"Mon\", \"Tue\", \"Wed\", \"Thu\", \"Fri\", \"Sat\" ], \"dayNamesMin\": [ \"SU\", \"MO\", \"TU\", \"WE\", \"TH\", \"FR\", \"SA\" ], \"monthNames\": [ \"January\", \"February\", \"March\", \"April\", \"May\", \"June\", \"July\", \"August\", \"September\", \"October\", \"November\", \"December\" ], \"monthNamesShort\": [ \"Jan\", \"Feb\", \"Mar\", \"Apr\", \"May\", \"Jun\", \"Jul\", \"Aug\", \"Sep\", \"Oct\", \"Nov\", \"Dec\" ], \"autoPopUp\": \"focus\", \"closeAtTop\": false, \"speed\": \"immediate\", \"dateFormat\": \"mm/dd/yy\", \"yearRange\": \"+0:+20\", \"fromTo\": false, \"defaultDate\": \"0y\" } }, \"edit-field-date-value2-timeEntry-popup-1\": { \"func\": \"timeEntry\", \"settings\": { \"show24Hours\": false, \"showSeconds\": false, \"timeSteps\": [ 1, 15, 0 ], \"spinnerImage\": \"\", \"fromTo\": false } } } });\x3c/script\x3e" }