Just to add my own explorations of this here. It worked fine and now does not. I installed 'include' plugin, but deactivating makes no difference. I get no buttons (for anything)- changing to HTML edit is unresponsive - 'locked'
Switch off all plugins makes no difference.
This happened on one of my WP 2.5 sites (5 on the same server). I have reinstalled this site and it still continues. All the other sites - the visual editor is fine in the same browser FF. It is the same unzipped WP2.5 used for all. I can only think that there must be something held in the database? I can copy within the server the wp-admin and wp-includes directories from working sites and again it makes no difference (even after full deleting these directories from copied to site).
One last thing - installing TinyMCE Advanced tells me "All toolbars are empty!" - like they don't exist - I also don't have and media buttons either
Any Suggestions?