I bought one of the early '08 Mac pros when they first came out, and at that time I added 2x2GB of RAM for a total of 6GB. Very recently, I added another 2x2GB (ordered from OWC) for a total of 10GB, to try an keep up with the increased strain I am putting the machine through. Since installing the ram, I have noticed a considerable drop in system stability... my intensive apps are crashing randomly, and a few times they have frozen OSX as well... Anyway, I am no expert on this stuff, and I don't know how to check if there is a problem with my ram. The system recognizes all 10 GB, and I installed the DIMMs according to the instructions on OWC (stock 2x1GB + my newest 2x2GB on top riser, and my older 2x2GB on the bottom riser). I ran tech tools deluxe, but it just said "passed". Has anyone heard of issues like this after upgrading RAM? Does anyone know how I can determine if my RAM is the issue? Thanks in advance everyone!