I've tried vertminer with my HD6970 (gigabyte).  If I set gpu-threads at 1, it works at about 60% of it's anticipated hashrate (yes, n-scrypt halving taken into account) based on what the the card does under windows using the precompiled windows binary.  When I set it to gpu-threads : 2, I get

Error -5: Enqueueing kernel onto command queue. (clEnqueueNDRangeKernel)
GPU 0 failure, disabling!


Any thoughts?