Have you followed the instructions in the Basic Troubleshooting Knowledge Base article? Note that some of these steps will not apply to you, as you can't start the browser.

thanks - I've tried all of this. If this helps to understand, this is the entire error report:

Process: firefox [172] Path: /Applications/Firefox.app/Contents/MacOS/firefox Identifier: org.mozilla.firefox Version:  ??? (???) Code Type: X86 (Native) Parent Process: launchd [112]

Interval Since Last Report: 45208 sec Crashes Since Last Report: 34 Per-App Interval Since Last Report: 0 sec Per-App Crashes Since Last Report: 26

Date/Time: 2012-03-24 08:40:39.854 -0400 OS Version: Mac OS X 10.5.8 (9L31a) Report Version: 6 Anonymous UUID: 5E812DA1-570A-402E-92E1-5F9DF8C09228

Exception Type: EXC_BREAKPOINT (SIGTRAP) Exception Codes: 0x0000000000000002, 0x0000000000000000 Crashed Thread: 0

Dyld Error Message:

 Library not loaded: @executable_path/libmozglue.dylib
 Referenced from: /Applications/Firefox.app/Contents/MacOS/firefox
 Reason: image not found

Please try reinstalling Firefox. Your personal data will not be affected. If that doesn't work, please consult this KB article.

I do not use Mac s but

Crashes
What would be useful is not the Mac crash info but the CrashID shown for the submission of the Firefox crash to Mozilla.

• see firefox crashes

Bookmarks as you are concerned about these (and other info ?)

• see backing up and restoring bookmarks
• backing up your information