Stuck on white screen on re-start . . .

Question

Often when I restart my Mac Pro with OS10.8.4 the white screen that precedes the Apple logo stays on indefinitely. Often this happens after Apple Mail freezes along with everything else (mouse or keyboard don't work, etc.). I have to shut down the computer to get out of the lockup.
The only way I've found to stop this cut off startup behavior behavior is to unplug the cable to my display and plug it in again. My display is an NEC LCD 3090WQXi. After plugging the display in again, starting up proceeds to the Apple logo in about a second or two and continues normal booting.
Any ideas?
Thanks in advance.

Answer 1

Run Disk Utility from the Recovery HD menu. Select the Macintosh HD volume in the list, then click on the Mount icon in the toolbar. If you still cannot mount the volume, then you will need to try reinstalling OS X:
Reinstalling OS X Without Erasing the Drive
Boot to the Recovery HD: Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.
Reinstalling OS X Without Erasing the Drive
Repair the Hard Drive and Permissions: Upon startup select Disk Utility from the main menu. Repair the Hard Drive and Permissions as follows.
When the recovery menu appears select Disk Utility and press the Continue button. After Disk Utility loads select the Macintosh HD entry from the the left side list.  Click on the First Aid tab, then click on the Repair Disk button. If Disk Utility reports any errors that have been fixed, then re-run Repair Disk until no errors are reported. If no errors are reported click on the Repair Permissions button. Wait until the operation completes, then quit Disk Utility and return to the main menu.
Reinstall OS X: Select Reinstall OS X and click on the Continue button.
Note: You will need an active Internet connection. I suggest using Ethernet if possible because it is three times faster than wireless.
Also see:
Reinstall OS X Without Erasing the Drive
Choose the version you have installed now:
OS X Yosemite- Reinstall OS X
     Note: You will need an active Internet connection. I suggest using Ethernet
                 if possible because it is three times faster than wireless.