Everytime I watch a DVD, I get these very faint, purplish-green waves that fade in and out of the screen. It isn't constant, but it's about 75% of the time I'd figure.

I am wondering if it's a bad cable, or if it's because I have too much stuff plugged in to one outlet, or what?

I don't have the lines during anything else. Watching TV, playing 360, or anything else...JUST while watching movies on my DVD player.

Any suggestions?

Kinda sounds like macrovision like but I doubt it is. Would help if you tell us the dvd brand and model.

It could also be some type of RFI interference. What kind of display, dvd player and other equipment do you have? How close are the speakers to display?

How is the dvd player connected?