Pure craziness: W530 will post with a DIMM in slot 1 **or** 3, but not both.

Question

I've been going nuts here, so I apologize in advance if this email sounds a litted harried.
I have two identical W530s in front of me. Both of them are i7-3820QM and are intended to support up to 32GB of RAM. So I went and ordered 32GB of RAM from Crucial and it showed up this afternoon. I promptly installed it all in machine A because I was in the middle of doing some work on machine B. Everything was fine with machine A.
After I finished my work on machine B I decided to move the four DIMMs over there for various reasons; machine B will be there final destination. I stuck them in, making sure to seat them nicely. The machine refused to post. I pulled a couple out. The machine refused to post. I put them back in machine A. Machine A posted. Something fishy was up with machine B.
To make a long story short, read the title of this message. This is seriously one of the weirdest things I have ever encountered with a piece of hardware. If you have all four DIMMs installed, the machine does not post. If you remove **only** DIMM 1, the machine posts. If you remove **only** DIMM 3, the machine posts. Slots 2 and 4 work just fine; whether they are empty or full or partially full doesn't effect a **bleep** thing. I've also tried this with 4GB DIMMs instead of 8GB DIMMS; same deal.
Just to be ridiculously clear, here are he configurations that work and those that don't. "x" means that slot is empty.
x x x x - fails, beeps (obviously)
x x x 4 - works
x x 3 x - works
x x 3 4 - works
x 2 x x - works
x 2 x 4 - works
x 2 3 x - works
x 2 3 4 - works
1 x x x - works
1 x x 4 - works
1 x 3 x - fails silently
1 x 3 4 - fails silently
1 2 x x - works
1 2 x 4 - works
1 2 3 x - fails silently
1 2 3 4 - fails silently
**bleep** is going on here? The BIOS isn't even giving error beeps in the failure modes. If I'm somehow being a total moron, please let me know; that is so much more satisfying than the idea of a machine that can't use all its RAM slots because of some weird hardware bug.
Thanks!

Answer 1

OK, so you've contacted service for repair on this system? I think that you've exhausted all user actions to correct.
W520, i7-2820QM, BIOS 1.42, 1920x1080 FHD, 32 GB RAM, 2000M NVIDIA GPU, Samsung 850 Pro 1TB SSD, Crucial M550 mSata 512GB, WD 2TB USB 3.0, eSata Plextor PX-LB950UE BluRay
W520, i7-2760QM, BIOS 1.42 1920x1080 FHD, 32 GB RAM, 1000M NVIDIA GPU, Crucial M500 480GB mSata SSD, Hitachi 500GB HDD, WD 2TB USB 3.0