I think I've worked out what the problem is - it seems to be due to some extra Javascript we added to enable keyboard shortcuts to work (one of my colleagues raised this a couple of years ago - http://cutesoft.net/forums/thread/4903.aspx).  Removing this Javascript fixes the toolbars in Firefox.  It would be useful to know how to get keyboard shortcuts (e.g. Ctrl-S for Save) working in Firefox but it's not a critical issue for us at the moment.

Thanks,
David