Why is my MacBook Pro (el Capitan) hanging while restarting?

[iMore Question]

When I restart, all I get is the screen with the Apple logo and the progress bar -- but the progress bar never shows any progress. I've held the power button down for a re-start, but that gets the same result. I don't even get to the password screen.

(Please don't tell me to go into safe mode; that is not an option until the OS boots.)

Thanks

 

[Raptor007]

I have held off on El Capitan due to issues with NAS devices not showing up in the finder and losing connections (iTunes library is on my 16TB NAS). I can say I have had what you describe on my MBP with Yosemite and sometimes I have to unplug my USB hub that is connected for it to fully boot up without delay. It was a fresh install.