So, I just had the original 300 GB hard drive fail in my aluminum 24" inch Mac running the latest update of Leopard. I wasn't able to save it using diskwarrior (diskwarrior said it was some sort of mechanical failure) but I was able to recover most of the data from it by booting from an external hard-drive. So I went out and purchased a brand new Western Digital Caviar Black 1TB drive. The install went fine, it found the drive partitioned it and installed Leopard successful. Then is crashed and disappeared when I left it alone to run all the software updates. I came back and the computer was stuck on "Restart Required" after downloading all the updates. I went to hit restart now, and the system just hanged, wouldn't do anything. So I hard powered down the system and restarted it. It came up with nothing, just stuck on the White Screen of Death. So I plugged the external drive back in and booted from it. Mac OSX couldn't find the drive and diskwarrior would crash if I tried to run it. I tried to boot up from the OSX start-up disk and it couldn't find the drive either. So I took the case apart and made sure all the connections were solid and the drive was mounted correctly. Everything looked fine so I plugged it in and it started up fine. Finished the updates and the iMac ran great. So I thought maybe it was overheating, so I've installed smcfancontrol and started to monitor the temp of the drive. I also took the mac apart again and sucked out any dust in the fans or vents. The drive never goes over a 105 F, so it doesn't seem to be overheating. However, this is where the problem is consistent: everytime the iMac goes into sleep mode, it crashes and the iMac is unable to find the hard-drive again. Unless I unplug it completely for 5 minutes or so. Once I unplug it, it finds the drive and operates like a champ. I think maybe there's an issue powering the drive back on? Anyone have any ideas?