Assume that you are logged onto a computer that is running Windows 8.1. You use the Fast User Switching feature to switch to a different user who is already logged on. In this situation, after switching users, you may see a large black bar on the right side of the screen. Additionally, the contents of some desktop windows or Windows Store apps may be blank.
After a short delay, the screen flashes, and everything appears normal.
Note In most cases, the screen will return to normal after one or two seconds. However, under some conditions it may take a little longer.