So this is annoying. 75% of everything I watch is either on Comedy Central or Cartoon Network. Both channels constantly say in the corner "available in HD!" but apparently my cable provider doesn't carry either. Sigh.
Silly question but: have you checked to see if there is an HD Comedy Central or Cartoon Network on your channel listing? It would be separate from the "normal" Comedy Central or Cartoon Network channels. The HD channels would likely be much higher channel numbers.