I've started having trouble with my trusty early 2008 3,1 MacPro, 10GB RAM dual 2.8GHz, four year old ATI Radeon HD 5870, bunch of drives. It runs the latest 10.6 version snow leopard as its the machine I use to run DVDSP, on those rare occasions I need to make a DVD. I have one 21 inch Apple monitor attached. So its not my main machine, but would like to get it going again. It boots up fine but after running a few minutes apps won't open up (beach ball), but finder seems to be working otherwise. A few minutes later the finder stops working. I can select shutdown but nothing happens, a minute later there is no response period. I've let it set for 30 minutes and nothing. Pushing the restart button will get it going again... but with same results. I have a portable USB drive with a year old OS clone, when I boot from it, I get similar results, slightly different timing. I do a safe boot and get similar results. I boot from the install CD and check all the disks with disk utility and it will run for hours without problems. The console log does not seem to show anything interesting, there is like a 2% CPU utilization when the freeze occurs, and the temp monitor is not showing high temperatures. Fans are running as normal. So there are a bunch of things I can try next, run a hardware test, open it up and look for fault lights, boot from a fresh install, disconnect everything, play around with RAM chips, look at the power supply, vacuum out the dust..... but I thought I'd check in here for ideas before spending a lot of time chasing my tail. .