I have lately been experiencing this problem on my Mac book pro 13" mid 2010 where it usually hangs and doesn't resume normal working. I try to restart the computer but it gets stuck at the progress bar. I have tried everything from safe mode boot, PRAM reset, disk utility first aid in recovery and time machine restoration but the problem persists until I reinstall OSX (it worked the last time at least). Now it has hit again. Need suggestions on how to deal with it. I'm using Mac OS X El Capitan and it gets stuck at approximately the 90% mark.
Could be due to kernel extensions you have installed, I had the same issue and posted a blog tutorial on troubleshooting and fixing something like that:
To troubleshoot, startup your Mac in Verbose mode (after you hear the chime):
Hold down one of these key combinations on your keyboard immediately after pressing the power button to turn on your Mac, or immediately after your Mac begins to restart:
- Command (
- Command (
Continue holding the keys until you see white text on the screen.
Starting in Verbose mode should give you enough output information to debug the problem even further. See my blog post for more in depth information and how I resolved my specific issue.
Cached versions of blog post:
Archive.org (WayBackMachine): http://web.archive.org/web/20161218201511/https://smyl.es/how-to-fix-mac-osx-stuckhanging-on-progress-bar-will-not-boot/