You may be a huge Firefox fan and experiencing a lot of crashes, especially when in Gmail, but can’t think of abandoning Firefox. The first thing you need to do to re-install Firefox to Troubleshoot Hangups is to ensure that you have backups of everything. 
Manual Backups of Bookmarks and Saved Passwords
I would highly recommend a manual backup of saved passwords and bookmarks. you can easily backup the bookmarks from Firefox directly, but to backup the passwords you need to first install the Password Exporter extension.
On installation, open the Add-ons window and click the Options button on the extension where you can simply export the passwords or encrypt it using the button.
When you backup the bookmarks, open up the Organized Bookmarks item on the menu and choose Backup from the “Import and Backup” menu.
Note: ensure to save both the files to a safe place before continuing further.
MozBackup
The MozBackup utility is also highly recommended since you can make sure that you have a total backup of everything in your profile. Here you choose Firefox in the first screen, then choose which profile to backup, when there is more than one.
Note: the default save location appears to be under “Documents”.
Thereafter, choose what you actually want to backup. It is recommended to back up everything as some issue could crop up in between the files.
Uninstall Firefox
This depends on your operating system, either you have to go into Add or Remove programs or “Uninstall Programs”, then find Mozilla Firefox in the list and choose Uninstall to get rid of any saved profiles.
Note: if you do a clean install with a new profile there are a lot less problems.
In XP or Vista, you can find your Profile folder by typing the following into the location bar:
%APPDATA%Mozilla
Finally, you can either delete it completely or just move that folder somewhere else. I would recommend to move it somewhere else in case you need the files again.
Re-install Firefox
Now you can simply re-install Firefox and begin with a completely clean browser. When you import your passwords or bookmarks, just use the same menus that you used above to backup, but choose the restore options instead.
