I've also had this happen when I was watching TNT, USA, Cartoon Network, and probably countless others I can't recall on Comcast.
Semi-Related: Back when GSN ran What's My Line? and I've Got A Secret (or a random G-T show) daily at 3AM, Comcast would cut off the end of I've Got A Secret/Other Show, usually only the goodnight and not a lot of time (so no big deal), to go to their own Paid Programming. All was well and good until DST hit. Someone at the office forgot to turn back the clocks on their machine, so instead of switching to their Paid Programming at 4AM at the end of the block, it would switch at 3AM as the block would start. I was quite disappointed at the time. I think it took them a couple of months to get their acts together.