Re: Please help! E P I C F A I L
Taking a quad to 500 Mhz isn't easy. I've never had one that liked going much over 450Mhz. The Q9300 is not a great clocker because the multiplier is so low.
Also, Gigabyte boards have more vdroop than most boards I've ever used, I stick with ASUS due to the Load Line Calibration feature - and easy pencil mod for vdroop. This eliminates the droop (or drop in vcore) during load which is a huge reason for instability.
You also didn't mention your cooling. I'm using high end custom water and the still one of hardest parts of overclocking a quad is controlling the heat. You might have seen some of the skilled quad overclocking reviews that put forth a misconception that it's easier than it really is. Hitting 500Mhz FSB is no easy feat though.