I was already wondering why there was such a big gap in voltages between the people running at around 4,4GHz and those above. With my chip, it seemed to be the case that when the core temperatures went over a certain point(around 60 degrees in my case) the chip all of a sudden needed a lot more voltage to keep stable further increasing the temperatures.
in my experience, lowering the voltage actually can improve stability of bulldozer at times, since this wil lower the temperatures. This way i could lower the voltage from 1,41V to just 1,38 while overclocking it only 50MHz less. It seems like you guys(or atleast panther) choose the high temp/high voltage route, whether consciously or not, and might in this way applied more voltage then needed.
Ofc, the difference between chips and their respective needed voltages might also be the explanation.
@cadaveca: thanks! This may very well solve the problem also. Now you mention it, I did not seem to have this problem when I still had 2 8800GTX's, and I also didn't notice it since i upgraded drivers(although thas wasnt really long ago, so its perhaps too early to totally rule out).