Open it up, test one board at a time, push lots of air at it and watch the temps.
I have tried everything. I actually found the problem, there is some issue you with the fan. I hooked up a small fan and it turns on and runs fine. So I went and got a brand new replacement fan and the problem is back. I have to hook the small fan up and leave it out of the erupter cube case, I installed the new fan and also ran the power wire out of the side of the case to the power supply. so far so good the block has been running for over 10 hours now. I have also found out that not only do android phones cause an issue with the Cubes but so do the google chrome books. If I have my cell phone or the chrome book connected to the wifi the cubes wont hash more then 1-2 GH if that.