Do me a favor just for curiosity's sake. Remount your MoBo, making sure that all standoffs are tightened snugly. That spooky problem may rectify itself. I had something similar happen to me. My system wouldn't get past RAM to Post when I had all 4 sticks in. I pulled on stick at a time and when I got to 2 sticks, it Posted. They were in the first two slots no less. Which they shouldn't have even allowed the system to Post since they weren't in the same series. When I remounted my board(found three loose standoffs) everything was corrected. Make sure no standoffs are hanging out under the board that don't need to be there either.
Just give it a try and see what happens. You won't be able to RMA on Sunday anyway.