The display has a horizontal bar that goes all the way across the screen and travels upward at about a 4 second interval. It starts at the bottom and goes to the top of the screen and then starts over at the bottom. It’s not problematic – just annoying.
This and other display artifacts can be annoying but are usually very easy to fix. In this case the user had been logged in for 42 days (not something you could achieve on a Windows machine) and merely locked the session at night. He is also on a soon to be upgraded Fedora 7 machine.
A simple logout and then login resolved the problem. This action resets the X11 display subsystem and usually will resolve the problem.
Another option that I did not try, because the first resolved it, would be to press Ctrl-Alt-F2 to switch to a different, text mode, console session, then press Ctrl-Alt-F7 on releases up through Fedora 8 or Ctrl-Alt-F1 on Fedora 10 or later. This would also serve the purpose of resetting the display, although it is not as all-encompassing as logout-login. If you try this first and it fails, do the logout-login.