Verify Permissions
diskutil verifyPermissions /
Repair Permissions
diskutil repairPermissions /
IT
Verify Permissions
diskutil verifyPermissions /
Repair Permissions
diskutil repairPermissions /
You can try booting from OS X recovery by holding CMD + R at the time of startup. Once booted from OS X recovery, select Terminal from the utilities and then at the unix prompt enter:
sudo diskutil unmountDisk /dev/(enter here disk identifier name)
sudo diskutil unmount force /dev/(enter here disk identifier name)