It looks like there may be a security issue when using the <base /> tag on pages. http://tinymce.moxiecode.com/punbb/viewtopic.php?pid=36516 From IE: Webpage error details User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; .NET CLR 2.0.50727) Timestamp: Fri, 27 Mar 2009 18:54:09 UTC Message: Object expected Line: 1 Char: 114105 Code: 0 URI: http://.../main/tiny_mce/tiny_mce.js