I think my problem may be different, but for what it's worth... I've had no problem with crashes until recently but I think I've found the problem.
I'm using DropBox to store the DB so that I can use FTM on both my MBP and iMac (both running OSX 10.6/5). It makes no sense to me to store backups in the same folder as the main file so I changed Prefs to store backups in the regular Document folder on each computer. Apparently FTM doesn't like that, at least when one is using Dropbox.
I changed the Prefs back to FTM's default backup and things seem to have calmed down. I don't think Dropbox itself is the problem because I also use it for my Reunion and 1Password databases without issue. For my system, at least, FTM seems to want that last backup in the same folder as the main DB.
For anyone who hasn't tried Dropbox, I can't recommend it highly enough!!! You get 2 GB free storage; my husband and I were so happy with it that we both paid for the 50 GB plan. DropBox gives both users extra free space if a referral link is used. If you give it a try and are so inclined, I would love to have my link used: https://www.dropbox.com/referrals/NTcxMjA4MjA5?src=global0