iMac hangs on boot even after reinstall
I have an iMac that hangs on boot, even after having its disk erased and OS X reinstalled from Recovery Console. I just tried to boot into the fresh install, and it's been stuck on the splash screen for about 45 minutes.
Disk selection comes up in 2 or 3 minutes if I hold option- I've been able to boot into an external drive with a known good clone, but only intermittently- once out of every three attempts.
It will open recovery console, but very slowly- takes 15 minutes or more.
I can't persuade it to run AHT from the OEM disc- the build-in CD/DVD drive won't accept the disc, and it doesn't seem to recognize the disc in an Apple external drive.
Anything else I should try? Is this a hard drive problem, or something deeper?