I cleared out all of my Core, Manufacturer and Bonus catalog stuff from ProgramData, as well as my User Catalog in the program's Data folder (which was in Documents on my machine) and started over from scratch.
Reinstalled the core catalog, redownloaded the bonus and manufacturer ones I got before, reimported the couple of SKP symbols I still had on my Desktop and added them to my User Catalog and no sign of the error again!
I suppose it's likely that it was only one of those files that was actually corrupt and I probably didn't need to wipe EVERYTHING out, so the tech probably will get back to me with less steps, but I'm one happy clam now!
larana's post in database disk image is malformed was marked as the answer