I was having a problem trying to get the TinyMCE editor to display when creating/editing posts in my WordPress 2.5 installation. Only the HTML version would display and Firebug would display an error saying: Illegal Character in the file: /wp-includes/js/tinymce/tiny_mce_config.php?ver=20080327
I read lots of posts with other people having problem with the TinyMCE editor, and eventually I found out that gzip compression may be causing the problem. I turned off gzip compression from the hosting control panel and cleared the javascript cache (/wp-content/updates/js_cache/) by deleting the file(s) in there.
This fixed my issue. Hopefully this will help someone else too.
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