It sounds like it's a monitor problem to me, (my old monitor was like this, I just slung it!!) but to be sure, either plug another monitor in to your computer, and/or plug your present monitor into a different video card and see what happens. If your present monitor works, plugged into another video card, then your video card is the problem. etc etc.
I must admit, I don't know of anywhere you could get it repaired, (if the monitor is faulty) but it could potentially cost you more than the cost of a new monitor. ie around £75-£80 for a new 17 inch crt. So.......the choice is yours...