I have a 27" iMac that just can't get past the grey start-up screen. It was running fine but wouldn't go to sleep, so I chose shutdown instead. Later that day I tried booting it back up and the grey screen with the Apple logo came up, then the grey progress bar below that (the one that appears when doing firmware updates, for example). The progress bar got about a quarter of the way through and then it disappeared and looked like it was going to complete the boot-up process. Nope. It hung forever. So I manually powered it down, waited a few minutes, and tried again. Same thing. I've tried several times, but it is always the same. I tried zapping the PRAM, but never got the chimes. I ran fsck -y but that did nothing. I tried booting from the install CD and that didn't work. I tried target disk mode with my laptop to see if the drive was at least working, and that didn't work either. WTF is going on? I'm going to set up an appointment with the Genius Bar, but I hate lugging that beast in, so I figured I'd give these forums a shot to see if someone can help. Thanks.