I couldn't change channel's using program guide or typing in the channel number. So I reset my DVR & fixed all my channel surfing issues. If this is the only problem you're having then reset you DVR or set-top box.
To do this: just hold in the power button until the display starts changing. It could take longer than expected. I think I held my power button in for close to 30 seconds. But, like I said, it fixed my problems.
Example of problem: pressed guide, arrowed up or down to channel I wanted to watch & hit select (OK). The problem is it didn't go to that channel; it stayed on the channel I was on. Then I would try to type in the channel # which didn't work either. I logged on & glanced through a few reviews & decided to just try & fix it myself which worked. Good luck!