There is no error message or anything.  The editor just seems to be in read only mode sometimes.  It even happens on this forum posting section; sometimes it will work fine but others it will not let me type in the editor at all.  The version of firefix is Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.8) Gecko/20050511 Firefox/1.0.4

Our website seems to not allow any editing with firefox while yours seems to sometimes allow and sometimes not allow editing.