My iMac is freezing on the startup page (the one with the apple logo and progress bar)

I had a similar problem. I had to wipe the hard drive clean, and reinstall system software and everything else from scratch to fix it.

I suppose it's a hardware trouble. Try to run Apple Hardware Test(extended) and see if it spits out the errors or not.

How to use Apple Hardware Test on your Mac - Apple Support

I've had a similar situation, but with very different symptoms:

1) Tried to wake from sleep - would not, so hard-powered-down.

2) After that, on bootup I'd get the grey screen with apple, progress bar, but no "progress" (even after an hour).

3) Booted to Recover, ran Disk Utility with no errors, but on normal bootup same results.

4) Booted to Recover and reinstalled the OS. It auto restarted after installation AND SAME RESULTS.

-- Left it on all night, woke to a 0% bar still.

5) Booted into Safe Mode...and it booted!

I left for work right after that, though, so I haven't tried a normal boot since, but Disk Utility is saying no errors, the partition (and files) are there and readable...but (so far) it won't boot normally.

Any ideas?

So after further testing, I have:

- Pruned my Extensions, PreferencePanes, StartupItems, etc.

- Removed all Login items from the Users/Groups pane

- Used OnyX to rebuild the caches

- Reset the SMC

The computer will still only startup in Safe Mode. I also cannot get the Apple Hardware Test to activate (and I can't boot from a CD because my optical drive stopped reading a long time ago).

I'd like to look at the startup logs and see if I can find where it's hanging, but I don't know where to start. I tried scrolling back on a few logs in Console but couldn't isolate where one startup and stopped and the next had begun.

Hi, did you manage to fix this? I have the same problem. I started an automatic update on my iMac and its now frozen on the startup screen. I've tried to restart it a few time but it just gets stuck.