Sorry I do not use Mac's but it seems likely that it is due to some problem in your profile. All the accounts will (or at least should) use separate profiles.

On the second faulty account try to create and use a new profile, that hopefully will stop it crashing. You will then be able to transfer information if necessary to recreate usable profile.

See

• basic troubleshooting_8-make-a-new-profile
• profiles

Try creating a new profile and post back with how you get on.

As far as I can see, the link gives instructions only for Firefox installed on a Windows machine. Since the problem I have stayed after re-installing Firefox, it suggests that the fault lies in one of the Firefox-associated files that are not in the Firefox app folder (eg. one of the files created by Firefox in /Library). This could be the .plist or profile files but I cannot delete (rm in a terminal command) them because permissions revent this.

Please Do NOT try to manually delete a profile; because you will destroy bookmarks and passwords. What I intended you to try, as a first step is create an additional profile.

If you are using a Mac to access this forum then the links I posted above should default to the Mac versions of those articles. (Maybe you are using a Windows Machine at the moment) You may also use the selector button; it has a plus sign +, and is on the left edge of the article page; to select the correct version.

Here are the direct links

• https://support.mozilla.org/en-US/kb/Basic%20Troubleshooting#os=mac&browser=fx12
  You will need to scroll it is a long article. I do not think I can link to the Mac specific sub section
• https://support.mozilla.org/en-US/kb/Profiles#os=mac&browser=fx12

I do not use a Mac, but would think creating a new profile for the problem account should solve the problem. Once you can get that account to open without crashing transferring the information over is the next step.

Please try the links again, or the revised links above, can you now see the article appropriate to a Mac rather than Windows ?

Take note of the instructions explaining

• how to find profiles both with and without running firefox
• and that by default you will have a profile called default.

Once you have created a new profile you should be able to find that without firefox running, and if you run Firefox with that new profile that is the one that you will find once accessing its location from within Firefox.

Post back with how you get on.

Just thinking aloud
Alternative,

• Backup info just incase, for each profile backing up your information
• install Fx 13 Beta, click new button to create new profile (Will automatically reset, create new profile, retain current bookmarks from the original default profile )

CrashID s may not help much at this point, we already know Firefox runs in some accounts not others.

Sorry, John99, but I have been working on the problem and deleted the Firefox profile from /Library/Preferences before I got your post advising not to do it. However, it worked although, as you suggested, I lost bookmarks and passwords. I actually moved the old profile file to my desktop so was able to restore the bookmarks from this. However, I had to enter in all the lost usernames and passwords (fortunately only a few). The bottom line is that, thanks to your advice that the problem was associated with a profile,I have now fixed Firefox for the second account.

Try to repair the disk permissions:

• http://thexlab.com/faqs/repairprocess.html
• http://guides.macrumors.com/Repairing_Permissions