Missing Channels with Mini Box

I just installed my mini box on Saturday, and it seemed to be working fine.  I was able to access all the channels I could when the cable plugged straight into my TV.  By Sunday, however, it only allows me to view a handful of channels.  For example, the lowest channels I can view (and that show up on my channel guide) are 11, 17, 21, 22 and 77.  So I have no access to CBS, ABC, NBC, FOX, etc.  I tried scanning for channels several times with no difference.  I also had the box check itself for issues, but that came back fine.  I even tried unplugging the box.  I don't understand why it was fine yesterday, but now I can only access a few channels.  I've noticed some people have had issues with the higher channels, but I have not seen anything yet about not having access to the channels under 20.  Any help would be appreciated.