OSX Black screen after upgrade. PolicyBanner.rtfd

So I have a small fleet of mac laptops and desktops that are mixed in with 500+ windows devices that I look after. Occasionally there is a issue that comes up along the lines of my laptop wont turn on... I did nothing.

So the symptoms are laptop boots like normal you hear the sound but after it may just flash a apple logo for 1/2 a second then you can only see the mouse moving on a black screen.

I have found that if you rename the PolicyBanner.rtf as to disable it using single user mode then reboot the mac will come back to life.

To test this fix is easy.

1. Turn off the offending mac.
2. Boot while holding Command key and S.
3. when you see the command line type "/sbin/mount -uw /"
4. "cd /Library/Security"
5. "mv PolicyBanner.rtfd/ PolicyBanner.rtfd-old
6. "reboot"

Now it should be working if you problem was the same that has been effecting my macs on and off for the last year. 

If it does fix you mac just run the process again and name you PolicyBanner.rtfd-old back to PolicyBanner.rtfd and your mac will continue to work. 

Done. :)