FIX GOOGLE GEARS problem Rated 5 out of 5 stars
Someone report a bug that GM cannot login after install Google Gears.
That is for Google Gears (GMAIL offline) not the extension.
You just remove all the sqlite files in your profile. Start Firefox again. (I do it because i donot know exact which file have problem). You can keep places.sqlite, cookies.sqlite, formhistory.sqlite for your personal info. It works that way!!!