Anybody use an optical cable to hook up their home theater to their TV?

For a while I was using RCA's to connect my Samsung HTIB (upconvert DVD player) to my Samsung LCD and it worked great, but it I had a small hassle to get audio to play through the home theater speakers. By the way, this is watching cable TV. Playing DVD's does not develop the same problem, only when I want to hear cable TV through the home theater speakers.

Tried using an optical cable (bought from Amazon.com) and though it worked and it got rid of my "hassle" now I get crackling from the speakers every now and then. Is this normal from using an optical cable?