Although I have only witnessed this error one time on one of my machines, a few clients have now started getting this. Doing the typical search has found the solution which actually worked on its first attempt.
I found that opening task manager and doing an end task on the Local Security Authority Process (3)-but this can be another number-some have been 5, would reboot the computer and clear the error.
Do the Microsoft 3 finger salute (Press Ctrl Alt Del buttons at the same time) . The Task Manager window opens. Then locate the process I mentioned above. Right click it and choose end task. Wait while the computer reboots.