Hey dean, Have you tried starting Firefox in Safe Mode? Hold down "shift" while Firefox is starting up. If the crash doesn't happen in Safe Mode, you should read [[Troubleshooting extensions and themes]]. There is also a lot of useful stuff in the [[Firefox crashes]] Knowledge Base article. If you've recently upgraded, you might want to check out [https://support.mozilla.com/en-US/kb/latest-firefox-issues#w_firefox-crashes-when-i-start-it this article] as well. Hopefully this helps!