I had mine mining for 8 hours on 6 cards, the PC then died and needed a hard reboot. It rebooted and came up with 7 cards working for roughly the same length of time.

I hard rebooted again and with 7 cards I get the CUDA error (never get the CUDA error with 6 cards).

I've also had it mining a few minutes and then get:

GpuMiner cu_k01 failed 6, the launch timed out and was terminated

It's all very random. I've tried -r 180 to try to prevent the 8 hour or so hard reboot issue but it didn't help.

I think I'm on GEN 2, I'll try GEN 1.