For the past week, I've been having issues with my Comcast cable where everything "works fine" except DNS. Even setting up my own caching name server did not work since UDP port 53 was a black hole as far as the public Internet was visible to me. Resetting the modem/router fixed it, only to have the problem reoccur anywhere from a few hours to a day later.
Last Friday I noticed BitTorrent running on my Mac, sharing only a CentOS ISO image, and killed it. I haven't had a problem since. Can anybody corroborate this apparently new tactic being used by Comcast to censor BitTorrent use?