Hi, had the same symptoms for Tiny, FCK, Xinhajtcreate wrote: SOLVED! (for me, at least)
I checked the server logs, and it showed this:
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[Thu Jun 19 05:31:02 2008] [error] [client x.x.x.x] SoftException in Application.cpp:544: Directory "/x/x/x/modules" is writeable by group, referer: http://www.xyz.com/x/x/editcontent.php? ... d=15&page=
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I checked the modules directory and it was set to 777. When I made it 755, TinyMCE started working immediately.
I'd mark the thread solved, but I don't know if this will solve the original posters issues as well... hope it does!
Jeff T.

Also changed to 755 and all working perfect now

Thanks!