MSI P67A-GD65 won't boot with dual channel

Hey guys,

Recently I RMA'd my MSI P67A-GD65 board (2nd time, 1st time was for faulty audio, 2nd time for BIOS update failure), and I just got it back.
Upon powering on my system, all fans and hard disks will spin up, but will shut off after about 5 seconds, with no beep or anything. I think I've narrowed it down to there being a problem with the board and dual channel. I've got 4 sticks of 2Gb G.Skill ram, if I put a stick in Slot 1 (blue) and another in slot 2 (black), I can power up and boot to windows no problem. However, if I put one stick in slot 1 (Blue) and another in slot 3 (Blue), which would be dual channel, the previous phenomenon occurs. I've tried updating the bios to the newest version but that makes no difference. It's really weird because before the RMA, there was absolutely no problems with running all 4 sticks of ram. I can't refund the board now because I've had it for nearly 2 years. Any ideas?

Thanks