I have an all X problem which I'm assuming is power related.
At first it was hashing away nicely for about 8 hours... then it stopped. After restarting, and then doing a full factory reset.... it will only run for about 1 hr before stopping.
power supply is a new Corsair CX750M with nothing else plugged in. Before I ran the cube on it... it was powering a 49 port USB erupter setup with no issues. :/
I will bet your all xs problem is due to one flaky board.
Try running one board alone and then add back one by one to identify the offending board.
I'm doing this now. Thanks for the suggestion. So far, 2 boards running with no problems. I'm adding a new board every 2 hours. I did notice when I took the boards out that a few of them had loose heat sinks. Hopefully tightening them will solve all my issues!