Do you also see messages like "sanity check, device is processing unknown work, device is missing queued job. device flushed (goes by too fast), failed to find work for queue results" in the bfgminer cmd window?
Interesting. When I first powered up I got a nice 700gh. After an hour I shut it down to switch power supplies, fired up, and saw some error messages and about 600gh speeds.
Shut it down, went back to previous supply, started up. Same.
This afternoon I shut it down, let it sit for 20 minutes to cool off, powered it up. 700gh, no errors I can see (I don't stare at it, just check every once in awhile). Solid as a rock.
One odd thing: I did notice the power supply high pitch frequency from the chokes was different. Maybe when the board is cycled hot it does a similar thing to what the old Singles did when they would power up more slowly. But letting it sit for a few mins seems to have restored it. Note it's been running for 6 hours now without a problem.
What are you seeing. Can you post the messages? Do they all do that, can you try shutting off the one that does for 15-20 mins? How does it hash?
C