Never had that problem. I use Time Warner.
A little tip just in case:
Be sure if you use the same line for your internet and tv, etc, your cable line should be going into your router first BEFORE any splits. Your HDTV/HD cable box is next, then the rest. The most important is your internet/router first. If you have too many splits, etc, you can also degrade your signal. Old cable lines can cause problems, incorrect cable lines that aren't capable of moving all the info your internet and cable sends/receives, bad or wrong type splitters (soo many cheap ones out there, it's best to get one from a cable guy, you can usually get them to just give them to you), and loose connectors all contribute to bad signals.