Yeah, if your GPU was ever running at that voltage you'd know from the sparks and smoke. Something caused HWMonitor to get a false reading. Also, any particular reason you're overriding fan speed control?
I set the fan speeds to go from 50% at 30c to 75% 40c to 100% at 50c onwards incase my rig was causing excessive heat build up. Seems to be keeping the Temps down with my long gaming sessions.
As for the malfunction with the voltage reading, is it a cause for concern?