ML350 G5 Won't Boot with 2 CPUS

I have never heard of this issue before, so I am thinking maybe it is specific to this rig.
I have tried several matching CPUs, and the rig won't boot. It boots fine with a single processor. So I know the CPUs are good. So socket or something on mainboard right? I switched the fans on the heatsinks, thinking maybe the one wasn't spinning correctly, like 5k RPM and not 9K or something and the BiOS won't let it boot. Nope! Both fans work fine and boot a single CPU. So, I tried each heatsink on a single CPU boot and one booted, the other the wouldn't.  I tried Heatsink #2 (the "bad" heatsink) in socket 1 and it gave the same error (won't boot).
I switched out ONLY the heatsink and it booted.

Has anyone ever heard of a heatsink causing the server to not boot?
Anyone have any ideas on what could be the cause besides a bad heatsink?