Ok, I'm new to Android and I screwed up. I used Titanium Backup (after rooting) to uninstall a few apps that didn't seem necessary, only to discover that I should have, at the very least, made a nandroid backup before doing any of that. The standard contacts app doesn't work any longer, although GO Contacts does. Anyway, I've been looking for an SBF to get me back to factory stock (my phone is only a couple of weeks old, and it shipped with 5.6.890).
I found a link to [SBF] Droid 3 Fastboot files (5.5.959 and 5.6.890) which seemed to have just what I needed; posters even indicated they had to re-authorize their phones after running it. I tried flashing with RSD Lite, but it failed with the error message "Size data returned by phone does not match what was expected." These files are supposedly specific to the Droid 3, so I don't know how that could be, but it happened on three successive tries. I tried removing my SD card, but it didn't help. The phone still boots normally, so no harm was done.