I have an older iMac (MA589LL) that I recently upgraded to 4GB and Snow Leopard which is running beautifully. I do have an issue with it though, and it's been occurring for a while: Whenever the machine goes to sleep and I wake it up, the monitor turns on just fine but after about 5 seconds it goes back to sleep. I have to repeat this about 3 times and then it is fine. It's an annoying issue but not a deal breaker as I can just turn it off. I searched for sleep issues/turn off issues and have not found anything. Any ideas here? NOTE: Issue occurred before the upgrades. I've also tried resetting the PRAM and NVRAM. I have also used different keyboards/mouses.