I installed Ubuntu 10.04 yesterday and was seemingly mining OK for awhile.
Today I re-setup Ubuntu 11.04 as a clean install due to some issues with setting up an LVM I'm having.
Long story short, I've resetup mining following the instructions on the first page of: http://forum.bitcoin.org/?topic=3359.0
Everything installed fine, and ./poclbm.py starts fine for a few seconds. Each of the 4 gpu's on the machine when tested individually will mine for about 10-20 seconds and then crap out with a "Verification failed, check hardware" message. I know all 4 GPU's aren't bad. Anyone know what might be worth checking in the software to troubleshoot?