Hi all, I finally got round to buying myself, what is hopefully my last major upgrade to my Mac Pro. I've flashed the firmware to be a 5,1 and bought a matched pair of X5680 3.33GHz. Tonight I popped these little bad boys into my mac, and it did't go as smooth as I thought it would. When I powered up, I got a red LED by each CPU/heatsink, no chime, the white power LED went on as usual, and got no display. When forced shut it down another red LED came on beside bay 1 of my hard drives. After calming down thinking I killed my Mac, I put back the original CPU's (E5520 Quad-Core 2,26GHz) and my mac is up and running again. I'm curious if there are any tips what to do. My Mac Pro is a 4,1 flashed to 5,1. Running Yosemite, has 32GB RAM, 1x1TB Crucial SSD, 3x4TB Hitachi, Mac edition Geforce GTX 680. Thanks in advance.