OK I just had this happen to me:
1. Power in house went out causing PC to switch off.
2. When power came back on and I restarted, the bitcoin database was corrupted and caused the machine to completely freeze on the "Loading Addresses" splash screen, since I set my bitcoin-qt to run as PC boots up. I tried restarting about 5-10 times til I realised it was bitcoin-qt that was doing it. It made the machine completely unusable. Couldn't even kill any processes. The log file was saying something about "PANIC" and to do database recovery. Very annoying. I know a corrupted bitcoin database is bad but I don't see why it should break the whole machine. Even ctrl-alt-backspace wouldn't work anymore.
So I deleted all the database files and now bitcoin-qt opens fine and starts syncing. However, if while it is syncing I go into options, don't change anything, and click OK, that causes it to immediately crash for some reason.
I am running version 0.5.0.1 BTW with Linux Mint 11.
Hope it helps.