Software :: Intel IMac Won't Boot Up - Freezes On Grey Screen Or Apple Symbol?

Got my 24" 2.4GHz iMac on release last year, with Tiger. Installed Leopard on it on release day.

The problem I have is that ever since a botched Boot Camp installation I've had endless problems with certain applications hanging during their startup (notably Image Capture) or refusing to quit (notably iTunes). Force Quit doesn't resolve these issues. Restarting doesn't work because Force Quit can't quit them so I have to pull the plug or otherwise force a shutdown.

Upon restarting I either get the grey screen that instantly appears, or, if I've pulled the plug and left it for a few minutes I can get to the Apple symbol but no spinner or any further start up action. Occasionally I get lucky, get back up and running, and all is well until the next crash.

All this started happening when I decided to try installing Windows on Boot Camp again. I've had it on here a couple of times since Leopard was released but usually end up deleting it eventually because either the Windows installation gets bogged down or I get bored with it and never use it. Anyway, this time, using the same discs I've always used (and yes, it's SP2, so it should be fine and anyway it's worked at least twice before) when I got to the 'restart to continue installing Windows' bit, I got the white screen and nothing happened. After an hour or so of praying and restarting endlessly trying to get a response, I finally got it to recognise my OSX installation and was up and running again. The Boot Camp volume didn't appear to be there and Disk Utility revealed zero problems whatsoever. Everything looked fine until these recurring hangs, refusals to quit apps and screwed up start-ups.

Any ideas? I don't have the expensive Apple support, but it's less than a year old! Of course, I realise that this means nothing to Apple, who seem to think I should pay a premium in order to have my machine warrantied by them for more than 90 days. Grr...

If I get it up and running I'm thinking I should just wipe the ENTIRE system absolutely clean and re-install Leopard and then use my Time Machine backup to put all my data back on (pricelessly valuable as I use the machine to work on my photography with), but I'm concerned that if there's a flaw in the System somewhere, a corruption, that installing the Time Machine backup will just reintroduce the error. On the other hand, if it's a deeply embedded and invisinle partition corruption from the bad Boot Camp installation attempt, that should be fixed by wiping the entire drive to reinstall Leopard, right?