Thanks to everyone for the yacminer tips. Got it nicely hashing along now on two of my rigs. I had the same issue as others with 4 x 280x, needed to drop the buffer to 1760 and drop R until no hardware errors. Now the rig is running @ 200 kh/s

So you have 4 x 280X's running at 50KHs per with 8GB RAM? May I have your final settings?

Thanks!
Jakiman's post nails it. My rig has one card @40KHs which is the only gigabyte , the other 3 cards are asus dc2t @ 55KHs. Don't know why one card needs to be dropped in buffer and -r, although I am very happy with the overall rate.
for now
