tucenaber and broker, you both need to upgrade to bitcoin 0.6.0rc2.
If you're on windows, look at my most recent post in this thread. The 0.6.0rc2 installer doesn't work right. You have to use the zip file.
I was sure I'd upgraded to rc2 but because the installer didn't work I was still on rc1 and had the problem you had.
I'm pretty sure I'm running bitcoin 0.6.0rc2. But i guess rc1 broke my bitcoin db somehow.
Im currently testing on another machine, where I switched directly from 0.5.2 to 0.6.0rc2 at block 167000. But still have to download 1000 blocks. If this works ill just copy the database to the other machine.
edit:
Does p2pool still work with 0.5.2 or is 0.6.0rc2 absolutely necessary?
I knew I shouldn't have upgraded to a unstable version on a productive system.