I experienced the "lockup during login" after upgrading my laptop to Firefox 2.0. Other users in our shop had no problem, but
I have a resolution:
1. Close Firefox
2. Navigate to /Documents and Settings/USERNAME/Application Data /Mozilla/Firefox
3. Inside the Firefox folder is another called "Profiles"
4. Move the entire Profiles folder someplace outside of the Mozilla folder.
5. Start Firefox and it will create a new Profiles folder and you will now be able to login to Zimbra .
To get your bookmarks back
1. Open "Manage Bookmarks"
2. Select File/Import (click "from file")
3. Navigate to the old Profiles folder and drill down to the Bookmarks.html file
I don't know what else may be missing as a result of moving the Profiles folder - not an expert here and I haven't explored further yet.
(Thanks to Ace Technology Group (
www.acetechgroup.com) for the tip. They are BIG Zimbra fans.)