Did you move Firefox's profile to somewhere other than the default location in your user library? I cannot think why Firefox deleting things from its profile would mess up other applications otherwise.

I installed Firefox on my MacBook Pro two years ago in the default location. The only thing that has changed since then is the incessant minor and major version updates that I allowed it to do. (SEVENTEEN updates in the last 18 months!) Please note, Firefox in and of itself is NOT deleting anything, however, when it locks up the whole system, any files that are open are either lost or trashed. After I power off the system (holding Command + Power Button for 15-20 seconds is the only way it will shut down) and turn it back on, when I go back to open Firefox it says something like "I can't find your tab/browsing history" While I really don't care about the history, I DO care when other files are trashed because of a Firefox issue! At this point I will try one last thing before giving up on Firefox... Completely remove Firefox and all Application Support files (including a dozen crash reports I've submitted, reboot, then install the latest Firefox. If that solves the problem, great! (And I'll NEVER update Firefox again... if it works, leave it alone.) If that does not solve the problem, then Firefox will be wiped off again, never to be seen again.

You could try SeaMonkey. I have been using that, and am pretty happy with it. There are no major issues. http://www.seamonkey-project.org/releases/

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

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 problems.

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

No corrupted fonts.

Just did a "Refresh Firefox" and will see how it goes in the next couple days.

8 days and no lockup while using Firefox since so whatever the problem was, I hope it is gone for good. However, wishing to keep it working as long as possible, I have completely disabled any update function and will stick with what works.

Nope... No good! 12 days and another solid lockup... gave it two minutes to see if it would come out of it but no joy. Even then it took more than half a minute holding down Command+Power to turn off the computer.

I've given Firefox as much rope as I'm willing so it's time to bail on Firefox.

Hmmm, I wonder, could it be a case of "too many cooks in the kitchen?" Along with the constant one-after-another updates... is there even enough time for any quality testing before release? Somehow I doubt it.