2. Restart your computer, beginning at the Start menu. (Yes, it's ridiculous that you turn it off by clicking Start.)
3. Do a System Restore to a date before the trouble started. Click Start - Help, then look for the System Restore information.
I just "fixed" a flickering monitor by Restoring my System to a date before I went on a vacation. ======== With respect to another problem, John-in-Kansas informed me that turning the computer off at the Big Red Switch (if you have one) can lead to problems when it's turned on again. I hadn't known that. So don't use the Big Red Switch.