Do any of the methods for calling up Force Quit work at all? http://support.apple.com/kb/ht3411

See if you can Start Firefox in Safe Mode {web link} While you are in safe mode; Press the <Alt> or <F10> key to bring up the tool bar. Followed by;

Windows; Tools > Options Linux; Edit > Preferences Mac; application name > Preferences

Then Advanced > General. Look for and turn off Use Hardware Acceleration.

Poke around safe web sites and see if there is still a problem. Then restart.

See if you have any crash reports;

Open a new window or tab. In the address bar, type about:crashes. Using your mouse, mark the most resent crash reports, and copy them. Now go to the reply box below and paste them in.

If you can't get Firefox to open; Open the file browser on your computer. Depending on your system, you need to find this folder; C:\Users\=<User Name>=\AppData\Roaming\Mozilla\Firefox Once you are there, look for a folder called Crash Reports. Inside are two folders; submitted and pending. Go into each. Copy the last 5 File Names in each folder. Remember, the last 5. Check the date/time. Post all the information in the reply box below. Forgot to add, with each file name, include the date and time created.