I have an early 2008 Mac Pro (2x 3ghz quad core upgraded w/ATI Radeon 5870 1gb video card). I bought 32gigs of ram (4gb sticks) from Mac Ram Direct back in early 2010 and earlier this year had a pair die. My initial call was to apple for troubleshooting and wondered about the likelihood of needing more than just a pair replaced. They at the time informed me that if a pair of RAM dies it is more than likely a bad batch and most companies would replace the entire order. Mac Ram Direct did not offer this and instead simply replaced the bad pair. A month or two went by and sure enough another slot went. Not wanting to go back and forth on the issue I gave it some time and now after 6months each pair of the initial 32gigs has failed (the replacement pair is working fine). I'm going back over this as I write to verify both sticks of each pair have failed. In either case I am getting some pushback from Mac Ram Direct over the cause of this issue. To quote: "I can go so far as to say that this is*virtually*impossible to occur without some other outside influence." This influence he believes to be cooling related. My mac pro sits on top of my desk in an air conditioned room that is always in the mid to low 70's at most during the summer and high 60's in winter. The desk is situated in the corner of my room with about 12inches behind it or more and about 3-4inches on one side with the rest being open. The fan works fine inside and I air dust occasionally. With the exception of avid which gets infrequent usage at the moment, the most demanding programs I use are all games on the windows side which themselves are 32bit. It is therefore a mystery to me how this issue is anymore than a case of bad product. I'm wondering how others would see it.