RAM slots (B1 & B2) don't work on ASUS ROG Maximus VII board

[LordInquisitor]

I've got an ASUS ROG MAXIMUS VII HERO motherboard with the LGA 1150 socket. About a year ago, RAM slots B1 and B2 stopped working. Right now I've finally got RAM in A1 & A2 working, but the manual recommends using A1 & B2 and, regardless, I've got two other sticks of RAM that I'd like to throw in there.
Whenever any working RAM stick is in B1 or B2, the computer won't boot and the POST thing will show 55. The MEMOK! button didn't help.
My CPU cooler is nearly unscrewed now, as I've tried these RAM slots with varying amounts of tightness with the CPU cooler (as well as without a cooler at all).
RAM slots appear clean to me, and I've blasted the ever-loving shit out of them with compressed air a few times.
The CPU doesn't appear to have any bent pins, either.
So did my motherboard just....stop accepting RAM in those slots? I can buy another one but I'd rather avoid that if I can. I've searched around online and can't find any solutions to my particular problem.
Sorry this post has been so long!

 

[InvalidError]

There are only four possibilities for this:
1- a broken trace or solder joint on the motherboard
2- bent or broken pin in the DIMM slot
3- bent or broken pin in the CPU socket
4- a fried control line on the CPU

The easiest way to find out if you can't see any tell-tale signs by eye is to try a different CPU on the board. If a different CPU works, then you know the problem is most likely with your CPU.