DOA PowerComputing Machines May Be Riser Card Problems

according to a note on Mike Breeden's Accelerate Your Mac!. "Another PowerComputing Mac owner says his DOA machine didn't need a new motherboard - just reseating the riser card. I've mentioned this issue at the site before but now I'm thinking many of the 'DOA' failures after CPU upgrades were installed may be due to an unseated riser card (in those models that have riser cards for the PCI slots/onboard video)."