I had this exact error (poclbm + deepbit) when overclocking my 3x 5830s yesterday (985/325). I would run for a while (no consistent time frame), then one of my cards would throw the "Verification Fail, Check Hardware" and go the command line (linux, ubuntu 10.04 LTS). I rebooted and ran it again. This time; a different card threw the error and stopped. I have to think that there's a power issue related to my overclocking (750W PSU). I have since tuned my cards back down to manageable 900/300, and I haven't seen an error since. So if there's another problem; I would love to hear it because I was getting 300MH+ with the higher GPU clocking.