In some cases, calling your cable/sat company and requesting that they update or reset your cable box may do the trick. If it's only the cable box, and not any other peripherals hooked up, then it's possible that the interference could be coming from the box. I realize an out of warranty situation is discouraging, but the television may not be the problem.
I have a LN-T3253H LCD TV. I have a Comcast cable box hooked up to it with an HDMI cable. When I turn on the TV and the cable box, I get a horrible crackling noise through the speakers for 2-3 minutes. The noise then fades and the TV functions as normal. This noise is the same regardless of volume settings, mute, etc.
I hooked the cable box up with RCA cables and the crackling does not happen at all. However, I don't think the picture is nearly as good with these cables as it is with HDMI.
I called Samsung and they told me they would not help since it is out of warranty.