Unstable in Dual mode?

I just installed 2x256 Corsair Twinx 3200LLPT. Ram timings 5-2-2-2. At first I used the wrong DIMM slots (2&3). Then I realized I needed 1&3 for dual mode. I had already ran 3dmark successfully mind you. I moved mem to slots 1 & 3 and it now says dual ddr at the bios screen. Now 3dmark crashes. The only change was switching memory modes. So now what, back off on timings? This sucks.

Or raise your vdimm.

~THT