Stability can be compromised based on NB temps but not voltages IMO, those pushing close to 47C on NB temps are very very close to the edge.

I think your going to find that this board just has a wall somewhere after 450 fsb with quads that induces instability.

I hit a wall with a celeron c2 rather low, 374 was max, would not do 375 even with the lowest multi. Yet 3.0g was stable....I'd like to say its bios related.