In most cases in this thread, it sounds like server issues. Sometimes it could be down to signal strength issues with cable, but if it goes down for two hours then comes back on it's own it's almost certain a poor server (that said, anyone can have issues - but if it's happening frequently it's a sign of a cheap server).
Have a look at your ECM times at peak times of viewing - it they're getting into 2-3 seconds then it sounds like the server is getting loaded and you could start to see glitching on lesser viewed channels.