Hello everyone, When I received my new 2012 iMac, I set it up using migration assistant to transfer my apps and settings from my MacBook Air (ran Mountain Lion) time machine backup. Everything went fine, and my new iMac worked flawlessly and was set up similarly to how my MBA was. I deleted the old MBA backups, formatted the external hard drive, and made time machine backup the new iMac. However, something happened recently with some file changes, that made me want to restore my iMac to a prior time machine backup. The restore process went fine; however, once the iMac rebooted, it was stuck on the Apple logo screen and the icon kept spinning...for over an hour. I tried resetting the computer, disk utility (verify and repair said disk was ok), SMC and PRAM resets...nothing worked. The iMac refused to start up! I even tried restoring it to a different backup and still, it wouldn't start. I thought it maybe had to do with the Boot Camp partition and considered deleting it, but Boot Camp worked fine and was able to start, it was only the Macintosh HD that wouldn't load. Needless to say, I used internet recovery and had to download Mountain Lion and re install, and that finally worked! Now I have to set the iMac up all over again. I'll be re installing all the apps and won't be transferring anything over from Time Machine. I'll even back it up using a new back up just to be safe. Any ideas on why this might have happened? ---------- Also, I was forced to use internet recovery to re install Mountain Lion as my ML USB install wouldn't work because the new iMac's are equipped with a different version of ML, and the version I was using was the one I downloaded from the app store.