You should be using another editor by now. Really.

But if you *are* still using FCKeditor then you may need to put this at the top of your page.tpl.php to force Internet Explorer to emulate an older version:

<meta http-equiv="x-ua-compatible" content="IE=EmulateIE9" >

This fixes incompatibilities between the separate FCKeditor library and IE10. As far as I know, the last FCKeditor release (2.6.10) is compatibile with IE9. Certainly it works fine with IE8, so you could also try EmulateIE8 if IE 9 emulation doesn't fix everything.

Strictly speaking this is not an issue with the Drupal FCKeditor module, but I thought this information might be useful for a few people. But, seriously, it's time to update to a newer editor (like CKeditor)...