Just a heads up if anyone else has a problem with this.
I use a Google libraries plugin and when activated it caused TinyMCE and plupload problems with FireFox 6. Couldn’t enter text or click on an icon in the editor.
If I deactivated the PLupload plugin TinyMCE worked fine.
I narrowed it down to the Google Libraries plug-in, deactivated it and both TinyMCE and PLupload work fine.
loading js or jquery from google libraries is a bad thing to do… and strongly recommended by the wp devs that you dont do it…
you should always use the jquery library (or js), if applicable, that ships with wp… otherwise you run the risk of conflicts… plugins get tested with wp and the version shipped with wp…
often the google api libraries dont work with noconflict directive either…