The Droid's getting up there in android years, so if this is the first time it's done it, I wouldn't worry about it too much. I would say it's time to reset it back to factory and get a fresh start, but it seems to have done that itself
Could have been some corrupt apps or a corrupt OS, maybe even a rogue app. Who knows, but obviously it's software related.
Well, I'm glad "somebody" besides me backs up their contacts occassionally
But if it continues to do this abnormal behaviour, time for an upgrade.