"File Download -Security Warning" in IE8 (editablefields_html content css code showing)

Confirming a field change with enter will open the "File Download - Security Warning" message in IE8 (see attached jpg).

When you download the file (file name consists of random numbers) and open it, you get something like this:

{ "content": "\x3cform action=\"/YOUR_PATH/editablefields_html/505/field_1_trans_cred/0\"  accept-charset=\"UTF-8\" method=\"post\" id=\"editablefields-form\"\x3e\n\x3cdiv\x3e\x3cinput type=\"hidden\" name=\"form_build_id\" id=\"form-58f37b33f2c58733dbb20b690f1a33d6\" value=\"form-58f37b33f2c58733dbb20b690f1a33d6\"  /\x3e\n\x3cinput type=\"hidden\" name=\"form_token\" id=\"edit-editablefields-form-form-token\" value=\"d3cd7ca2deb19cdfdbe3b50f02c624f6\"  /\x3e\n\x3cinput type=\"hidden\" name=\"form_id\" id=\"edit-editablefields-form\" value=\"editablefields_form\"  /\x3e\n\x3cdiv class=\"form-item\" id=\"edit-YOUR_FIELD-0-value-wrapper\"\x3e\n \x3cinput type=\"text\" maxlength=\"10\" name=\"YOUR_FIELD[0][value]\" id=\"edit-YOUR_FIELD-0-value\" size=\"12\" value=\"12.00\" class=\"form-text number\" /\x3e \x3cspan class=\"field-suffix\"\x3e%\x3c/span\x3e\n \x3cdiv class=\"description\"\x3e\x3cstrong\x3eYOUR_FIELD_NAME\x3c/strong\x3e YOUR_DESCRIPTION\x3c/div\x3e\n\x3c/div\x3e\n\x3cdiv class=\"add_validator\"\x3e\x3cdiv class=\"item-list\"\x3e\x3cul class=\"add_validator\"\x3e\x3cli class=\"first\"\x3e\x3ca href=\"/YOUR_PATH/admin/build/validation_api/fields/add?form_id=editablefields_form\x26amp;form_field=YOUR_FIELD%5B0%5D\"\x3eAdd a validator to YOUR_FIELD[0]\x3c/a\x3e\x3c/li\x3e\n\x3cli class=\"last\"\x3e\x3ca href=\"/YOUR_PATH/admin/build/validation_api/fields/add?form_id=editablefields_form\x26amp;form_field=YOUR_FIELD%5B%25%5D\"\x3eAdd a validator to YOUR_FIELD[%]\x3c/a\x3e\x3c/li\x3e\n\x3c/ul\x3e\x3c/div\x3e\x3c/div\x3e\n\n\x3c/div\x3e\x3c/form\x3e\n", "__callbacks": [ "Drupal.AjaxLoad.loadFiles" ], "scripts": { "core": { "misc/jquery.js": { "cache": true, "defer": false, "preprocess": true }, "misc/drupal.js": { "cache": true, "defer": false, "preprocess": true } }, "module": { "modules/modules/admin_menu/admin_menu.js": { "cache": true, "defer": true, "preprocess": true }, "sites/all/modules/ajax_load/ajax_load.js": { "cache": true, "defer": false, "preprocess": true }, "sites/all/modules/nice_menus/nice_menus.js": { "cache": true, "defer": false, "preprocess": true }, "sites/all/modules/panels/js/panels.js": { "cache": true, "defer": false, "preprocess": true }, "sites/all/modules/validation_api/validation_api.validator_link.js": { "cache": true, "defer": false, "preprocess": true } }, "setting": { "basePath": "/YOUR_PATH/", "admin_menu": { "margin_top": 1 } } }, "css": { "all": { "module": { "modules/aggregator/aggregator.css": true, "modules/modules/admin_menu/admin_menu.css": false, "modules/modules/node/node.css": true, "modules/modules/system/defaults.css": true, "modules/modules/system/system.css": true, "modules/modules/system/system-menus.css": true, "modules/modules/user/user.css": true, "sites/all/modules/cck/theme/content-module.css": true, "sites/all/modules/ctools/css/ctools.css": true, "sites/all/modules/nice_menus/nice_menus.css": true, "sites/all/themes/YOUR_THEME/nice_menus.css": true, "sites/all/modules/og/theme/og.css": true, "sites/all/modules/panels/css/panels.css": true, "sites/all/modules/cck/modules/fieldgroup/fieldgroup.css": true, "sites/all/modules/validation_api/validation_api.css": true }, "theme": { "sites/all/themes/YOUR_THEME/html-elements.css": true, "themes/zen/zen/tabs.css": true, "themes/zen/zen/messages.css": true, "themes/zen/zen/block-editing.css": true, "themes/zen/zen/wireframes.css": true, "sites/all/themes/YOUR_THEME_DIRECTORY/zen.css": true, "sites/all/themes/YOUR_THEME_DIRECTORY/layout.css": true, "sites/all/themes/YOUR_THEME_DIRECTORY/YOUR_THEME.css": true, "sites/all/themes/YOUR_THEME/YOUR_THEME-fresh.css": true } }, "print": { "module": [  ], "theme": { "sites/all/themes/YOUR_THEME_DIRECTORY/print.css": true } } } }

I don't really want anybody to experience this... Ideas on how to avoid this? Can anybody reproduce this bug?