*Taking a while to cache the firmware (black screen with progress bar)
*have it working then it just stops for no reason
*internal ROM with the firmware is OK since your still able to turn it on and initiate the restore with iTunes.
Something is causing the hard drive to loose its data.You get lucky every now and then and the restore writes to the hard drive and it reboots to a working state but then the hdd eventualy fails agian. Its probably defective, you should take it in to have it replaced.