Hum when cablevision is plugged in to tv


I am trying to watch & listen to DVD's through stereo but get hum out of speakers when the cable tv is hooked up to back of tv. When I disconnect it the hum goes away. Never had this problem before until I moved to this apartment in big house. Any advice would greatly be appreciated.
romad
I called the cable company they are going to come out on the 3rd, hopefully they can ground it better or I will try some of your suggestions. Thanks very much Agon members for your help.
This question has come up numerous times. Here is a copy of my solution which I have posted before:

I had this same problem. Here are the two parts you need, total cost $11:

http://www.radioshack.com/product/index.jsp?productId=2103063&cp=&kw=300+ohm&kwCatId=2032057&parentPage=search

http://www.radioshack.com/product/index.jsp?productId=2062059&cp=&pg=1&kw=ohm&kwCatId=2032057&parentPage=search

Connect the cable coax wire to the transformer/splitter.
Connect the wires from the transformer/splitter to the 75-ohm coax combiner/splitter.
Connect the 75-ohm coax combiner/spltter to the input on your TV.
This was done for me by the cable TV guy. Worked like a charm. Why? I don't know. I guess it breaks the ground loop.
This approach works to block the DC offset but it does not eliminate it. Get the cable company to fix the ground.

Kal