As title says.
I've tried every BIOS/ME/BMC/FRU package that's been released to date.
I've got a S2600COE based system (Intel P4308XXMFGN chassis) with an NVIDIA GeForce GTX 670 (2GB) by PNY and you cannot reboot with it.
The system will start fine from cold, but won't reboot - you just get a weird sequence of 5 (or 8) odd beeps.
If you disconnect the power it normally boots ok.
System currently has :-
BIOS : 01.06.0001
ME : 02.01.05.107
BMC : 1.16.4010
FRUSDR : 1.09
My current video BIOS is :-
GPU Device Id: 0x10DE 0x1189
PNY GeForce GTX 670 PCIe 3.0
For what it's worth, I've also tried an EVGA GTX 680 (2GB) card and this was exactly the same.
Though, the Kepler-based K5000 card works perfectly.