The basics: Mac OS X 10.10.1 Yosemite, 10 GB RAM. Thunderbird version 31.3.0 (though the same thing happens when I try earlier and later versions). Symptom: Thunderbird crashes within a few seconds of starting it up. I have enough time click on a menu or two, perhaps glance at a message, then it crashes. Attempted solutions: - Starting Thunderbird in Safe Mode. - Starting the Mac in Safe Mode. - Deleting ~/Library/Preferences/org.mozilla.thunderbird.plist and ~/Library/Preferences/Thunderbird, deleting the Thunderbird application, emptying the trash, and reinstalling Thunderbird from mozilla.org. - Using Yosemite Cache Cleaner to scan the hard drive for viruses, and to deep-clean all System and User caches. - Booting from the Recovery partition, repairing disk permission, and repairing the filesystem. The only time Thunderbird has semi-stable is just after I've deleted all preferences, started it up, and I do the initial set-up for my e-mail account. Everything appears normal, and my list of IMAP folders appears. But shortly after that Thunderbird crashes again, and keeps crashing at every subsequent restart. This is a problem that developed last Wednesday, Dec 24; prior to that the program ran just fine. No other program on my computer at work is showing these symptoms. Thunderbird works on my Macintosh at home (same software versions) and on my Linux computer at work. I'm at a loss of what to try next. Any ideas?