I have a Dynex tv/DVD combo the cable guy connected it and it works to turn on and off the tv and cable box except after I turn it on I can change the channels all I want, but once I find something to watch and decide to change it after watching, I cannot change the channel (yes it is on for the cable box not tv) so I rebooted the cable box and it worked to change the channels then it happened again where I can't change the channels again. Please help.