Here is the info:
Lightroom version: 2.2 
Version: 10.4 
Application architecture: x86
Physical processor count: 2
Processor speed: 2.1 GHz
Built-in memory: 3072 MB
Real memory available to Lightroom: 3072 MB
Real memory used by Lightroom: 603.6 MB (19.6%)
Virtual memory used by Lightroom: 969.1 MB
Memory cache size: 567.5 MB
Application folder: /Applications
Library Path: /Users/ekr/Pictures/LR2_test/Foobar/Foobar.lrcat
I have just ignored my database and reimported all files one more time. It seems to work, but I lost all my collections. So the problem was with the existing database. I had the same or similar problem with 2.0. After that I tried to open the old database again, with the same result. After deinstalling (removing) 2.2 and reinstalling 2.1 I could use the existing database. Part of the problem is that I had quite few problems with the database in LR when upgrading LR and I also find LR somewhat lacking in error messages so I start to be a bit anxious about updates. On the other hand I'm a software developer/analyst myself so I know that it's not easy.
Erik, which version of OS X do you have installed? And system details would be helpful, too.