I've got a 21.5", late 2011 iMac which has been acting up lately: after a normal shutdown, the computer would hang at the Apple logo, with the spinning 'loading' wheel below it. I managed to fix this issue the first time by booting into Recovery HD and, through Disk Utility, verifying disk permissions and repairing them (diskutil found about 30 errors at that time). That made the computer work for a few days, but after restarting again yesterday, the problem returned.
I went back into Recovery > Disk Utility, and verified the permissions, but found no issues. I still ran a permission repair, and even verified the disk, only to find out that the disk is "OK". I ran the disk repair tool, and then restarted. The machine still hangs on startup.
The machine isn't affected by the Seagate drive replacement program, but unless I'm booting into Recovery HD, the drive doesn't make any spin-up or head clicking sounds.
Is there any other solution here?