I need help with solving a computer monitor problem.?

I have the Acer AL2016W LCD flatscreen monitor. From time to time, this flickering, shimmering vertical streak pops up on the screen. When I take a screen shot and paste the shot in PSP, the streak isn't there, so it has to be the monitor. Does anybody know how to remedy this monitor problem?
Update: It's a vertical strip that covers whatever is on the screen. Like I said, it is a problem with the monitor, or the graphics card. It only appears from time to time, and sometimes it disappears without incident.
3 answers 3