My PC will only post with one of my 2 Corsair Dominator 2 GB 1600 mhz sticks in slots A2 or B2 (both work when installed alone in these slots).I cannot use A1 because it's blocked off by my gigantic heatsink and B1 doesn't seem to be working with either sticks.What could be causing this?I recently tried resetting CMOS but witch just the jumper switch it didn't seem to be working (date and time settings are the same).I run memtest on both sticks with 3 passes in B2 slot but when put in together even memtest won't recognize them.Any suggestion?(i'm new at this)