Two suggestions:

1) If you think it is the cable, change it out. I know cable isn't that cheap, although Radio Shack Gold series works for me, but maybe you can swap cables with a friend. Just a thought...

2) Do you have the components plugged directly into your wall socket? Also, do you have lights on dimmers in the room? Without any type of filters on the line, both of these things can cause snow in your picture. Try watching something with all the lights completely out. You may also want to experiment with different sorts of power filters.

Hope that something along these lines clears up your problem. Don't be afraid to try out something different. Have fun!