Did the Cable Guy Do It?

I recently had the cable tech come in to fix a problem with poor picture on some channels. He fixed that problem just fine by replacing the splitter outside and running new cable to the box. However, now I'm getting a loud humming sound when I fire up the receiver that is apparently being caused by the DVD player audio connection. Whe I disconnect the audio out from the dvd player it goes away (along with the sound). I tried replacing the cable to the dvd player, but that's not the problem. Any ideas what could be causing this? Could it be the dvd player?
Go outside and look where the cable company's cable attaches to the house. Do you see something that looks like a splitter with a wire connected to it. This a a lightning arrester. Does the wire that is connected to the arrester go to a ground rod driven close to the arrester. If yes more than likely this is your problem, a ground loop. Disconnect the wire from the arrester and see if the hum is gone. If is is gone you still will still need lightning protection. Run a new wire from the arrester to your main incoming water line. Use a water pipe ground clamp. If you cannot get to your main water line connect it to a cold water pipe of your water system.

Jim is right, it most likely is a ground loop. You can also buy ground isolation transformers or the Mondial MAGIC, both of which go in line with your cable.
Thanks guys, it turns out it was a faulty ground, or more accurately, no ground. He forgot to connect the ground wire when he did the installation. Simple fix and the hum is gone. I appreciate your help.