Last month i purchased 4 GB (2 X 2GB) RAM for my brand new Mac Pro, to add to the 4GB of Apple's RAM. I just pulled out OWC's RAM because of operating temperatures of 260 degrees! My new ATI 1900 graphics card (which is located just above the OWC RAM) overheated and went buggy & had to be replaced. The RAM temps remained high (for the top card only) until I pulled out the OWC RAM. Now, the temps run about 140 degs. I'll call OWC for a solution in the morning. I suggest you get the free iStat temperature widget.