If it is the factory power supplies like mine, they are getting weak on output. I reduce my frequency to 1300 and this seems to solve the problem. I am giving up a little speed, but gaining over all. I am about to order some new upgraded power supplies!
Mtnminer
I've managed to get both of my units hashing at 200Gh/s+, however occasionally the hash rate will drop to 35-40Gh/s without warning with very high HW error rate. A reboot fixes the problem, but I'm forced to reboot the machines 2-3 times a day (and lose valuable mining time!). This happens on both miners.
Any thoughts?