Hi guys, I'm hoping someone can point me in the right direction because im out of ideas. I wanted to upgrade my macpro 4.1 to 5.1 by swapping the cpu's to 2 x5680's. The upgrade went fine at first, but after 3 days it started freezing like 10 sec after boot. I swapped every piece of hardware in the mac with something else but it wouldnt help, so i went back to the CPU's. Removed CPU B from socket B and all is fine, no freezes. Placed CPU B in Socket A, all is fine no freezing. Putting back in both cpu's: Bam, freeze within 10 sec, the mac wont recover from the freeze. I thought it might be broken B socket so I just put back in the old CPU's, and all is fine. I'm out of idea's... anyone?