I have the same issue in 2.5.
Visual editor nor HTML editor work when “use visual editor” is turned on. If I shut the option down, I can see the regular html editor.
-> Both my sites upgraded from 2.3.x (same version) and they’re on the same hosting account.
-> One of the sites refuses to display the editors, the other works fine.
– IE6 shows both working.
– Firefox 2.0.0.13 shows one working and the other fails.
What I tried:
* clearing browser cache.
* deactivating plugins.
* clearing wp-content/cache.
* uploading 2.5 source files again in WP-includes and WP-Admin.
None of it worked.