Ok guys, here is help! Yesterday I was setting up my rig with several 5830 under windows XP and hat the exact same error: "Verification failed, check hardware!" Wenn I had just one card plugged in, everything was working perfectly fine.

It has something to do with the Kernel32.dll which is a library in windows. My problem was, that I had a fresh Version of Windows XP SP1 running without any updates. So all I had to do was updating to SP3 and now it works just fine with all cards running simultaniously. (updating to SP3 should be enough, however I installed all other updates too, just to be safe).

I hope this helps you solving this problem.