Well, I probably found out what's wrong. I wrote a script to add 1 to each of the member IDs, but apparently during the course of 5,000 replacements, the script hiccupped a lot. I guess that's what I get for trying to tame the beast.
The best course of action may be to revert to the saved version of the database from before the re-sync. All changes since we switched forums would be lost (which, based on the stats, is only about 20 changes. I vote yes.
Oh, still gotta figure out how to add 1 to the ID's.

:sad:
By the way, the I mean "database" as in data on a hard drive... not the script itself.