Originally Posted by
this_is_gav
On my UD5 one of the sticks of RAM was faulty (Corsair PC1333 9-9-9-24). The BIOS never saw it but CPU-Z did.
Going through all the sticks individually showed the problem (instability was doing my head in and Memtest wouldn't work on that BIOS) and the PC wouldn't even boot with only that stick installed.
The board itself died soon afterwards, but both the RAM and board were faulty and replaced by Scan (the CPU was fine, as I sent that back too as the memory controller is on the CPU of course), but I'm fairly sure this particular issue was the RAM module itself in my case.