You can try to disable hardware acceleration in Firefox (you need to close and restart Firefox).

• Firefox > Preferences > Advanced > General > Browsing: "Use hardware acceleration when available"

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

You can check for corrupted and duplicate fonts and other font issues:

• http://www.thexlab.com/faqs/multipleappsquit.html - Font Book 2.0 Help: Checking for damaged fonts
• http://www.creativetechs.com/iq/garbled_fonts_troubleshooting_guide.html

Thanks but I can't even access the menu when I try to start Firefox so this didn't help.

Can you start Firefox in Safe Mode by holding down the Shift/Options key?

Yes, it will now open in safe mode.

I went in and disabled the hardware acceleration then closed. I tried to open it (not in safe mode) but it still crashes.

Can you use the Profile Manager to create a new profile?

Try to create a new profile as a test to check if your current profile is causing the problem.

See "Creating a profile":

• https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles
• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues

If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over the problem

• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox