Although you're using those Corsair Dominators and I'm running these DDr2-1000 Crucial Ballistix, you may want to look at my recent thread on the Memory forum.
My two favorite OC settings had been made with a single 2x1GB memory kit. I added a 2x512 kit boosting it to 3GB.
In about an hour or two, I'll be able to confirm that timings need loosening when you do this.
There was some skinny around these forums that the 680i chipset didn't play nice with all four slots filled. It seems to be "almost OK" with these Crucials, but I hadn't thought to recertify stability with the double-ORTHOS Blend-Test. I only re-tested with "small-FFTs" and "Large FFTs."
So I'm testing with the 3 Ghz over-clock settings, with the timings loosened from 3,3,3,6 to the 3,4,4,8 timings I had for the 3.2 Ghz settng. This will mean (probably) that I'll need to loosen the timings for the 3.2 setting to something like 4,4,3,8.
I can always drop back to the 2GB kit leaving the other two slots vacant. It's really a catch-22: XP-Pro 32 doesn't recognize more than 3GB, but with 3GB I may need to loosen timings. And if I "wanted to go all the way" and still keep two slots vacant, I could buy that new GSKILL 4GB 2x2GB kit for something like $130 at NewEgg. So I'm x-ing my fingers that i just need to loosen the timings and learn to live with just a tad less performance.
You didn't say whether these Dominators are filling four slots or two . . .