Posted 15 July 2009 - 10:11 AM
First, check the VGA plug (or DVI). Are their any missing or bent pins? If not, try wriggling the plug while it is plugged into the computer.
If you still have the same problem, your monitor is either dead or dying. If its an old LCD, its common. CRT's will do the same thing.
If you still are not convinced its dead, try plugging it into a different computer.