I have a Dell Trinitron monitor, about 4 1/2 yrs old. It starting showing marks on the screen that look like an Etch-o-sketch, like someone took an instrument and scribbled all over the screen. It looks like scratches but from the inside. I believe it is traisl from the mouse movements. I have lived with it but the problem is getting worse and it is now very hard to look at the screen anymore. I use a screen saver, and my monitor is set to turn off after 30 mins of inactivity. What could be causing this and is there anything that can be done about it?