wysiwyg / visual editor gone / not working

Hi,

can anyone please help me with this problem?
In one of my blogs the wysiwyg / visual editor is suddenly gone!
The tab “Visual” is there but the buttons are gone and the text is shown in html.

What i′ve tried so far:
– searched google and this forums for help
– cleared browser cache / use other browsers
– checked the profile/user optione, “Disable the visual editor when writing” is off, turned it on/off several times
– deactivated all plugins
– activated standard theme “Twenty Ten”
– deleted all files except wp-config.php and uploaded a fresh copy of wp 3.0.4

Nothing worked ??

Any help would be highly appreciated – Thanks!

Greetings
Martin