If the monitor's that old, it's possible that you've been "stretching" it with the high resolutions and refresh rates your graphics card is capable of.
I'd guess it's on its way out - but without actually seeing it, it's difficult to tell.
Try running the card with conservative settings - say 1024x800@16-bit colour, and adjust the refresh rate to 70Hz or so.
Hope this helps CitrixEngineer@yahoo.co.uk