Second display problem with 10.9.4

I had the same issue so I called and paid for apple care… was an awesome experience, thought I would share the value:

After all of the typical troubleshooting steps failed to resolve anything... he walked me through the following:

restart in safe mode:

-shut down your laptop.

- press and hold shift key, press power key, keep holding the shift key until the apple and spinning gear are on the screen, then release the shift key.

Login.

Finder, GO, Computer, MacintoshHD/Library/Preferences: drag anything with “windowserver” filename to trash.

Finder, GO - hold down the option key (you will notice the list changes to include Library), Library/Preferences/ByHost: drag anything with “windowserver” filename to trash.

Empty Trash (if anything left in trash, then go Finder, Secure Empty Trash)

Then restart.

This worked for me. Good luck.