hi guys... I have a mac pro early 2008 with the 2 quad core 2.8 Xeon processors. A few weeks ago something very strange started happening. I would turn my computer on and it wouldn't boot. Instead I would get a front blink light. I immediately thought it was a RAM problem so I started moving RAM around to identify a problematic chip. My current configuration is top riser 2gb OWC-dimm4 2gb OWC-dimm3 2gb OWC-dimm2 2gb OWC-dimm1 bottom riser: 2gb OWC-dimm4 2gb OWC-dimm3 2gb OWC-dimm2 2gb OWC-dimm1 This is what I have found: The computer will work and booth as if nothing ever happened ONLY when a) bottom riser dimm 4 and 3 are unoccupied b) I use the 1gb chips in those two slots that came with the mac originally If I put any OWC ram in those slots they computer won't boot. I even bought another riser to make sure and I get the same thing. Right now I am running at 14gbs because of this. I am positive is not the RAM as all the chips work when placed on other locations. Any ideas or tests I can run? I am kind of disappointed as I thought I would be running at 16gbs right now. Thanks.