You'll probably get a better response if you move this to the tech section.
Have you tried adjusting the monitor? It's hard to tell with just a snapshot, but I've something that looked like that and adjusting it fixed it.
Depending on the type monitor you should have adjustment pots in several locations. There's usually a sticker showing which one does what.
If you're not experienced with monitor work then be cautious, you are working close to some high voltage stuff back there.
- JM