At first, nothing I did worked. I deleted these folders:
- blocks
- chainstate
- database
I started up the 0.8.1 client again and let it sync. It got up to around 7000 blocks left and just stalled, never updating the rest. I left it for DAYS to catch up. No luck.
So, I did it all over again. Same misery. It simply wouldn't sync up to the current block and was always around 7000 blocks short.
On another computer I downloaded and installed the bitcoin-qt client and ran it. It took forever and a day for some reason (as you can tell from the date of my original post and the date on this one), but eventually sync'd up. I copied my wallet from the first computer to the second and it worked. I also copied the folders listed above to the first computer and ran the bitcoin-qt client again. That finally worked.
No idea what the problem was, but that's how I got it solved... eventually. Hope it helps some poor sod with the same misery.