PVR will not record certain channels

I have a Pioneer DVR-533H-s that I am starting to have trouble with. It wont access/ record some TV channels. When I access the on screen "TV Guide" the machine gives me correct information for all the cable channels that are availble in my area and for which I have subscribed: but it will not allow me to tune to channels 20 -27! It will tune in and record all the other channels but not those 8 channels.
I know the cable is delivering the signal because I can access the channels if I tune to the regular stereo channel and bypass the PVR.
I have gone to "set-up" and run the program multiple times with no change in results (though I must admit I can not get the PVR to rescan the channels, and I would like to be able to do that). I have made sure that the channel display and the channel tune are compatable and I have unpluged the power and left the machine off for over 24 hours. Oh yes I have also bought a different PVR and it can access the missing chanels but I want to return it because it does not have EPG (No TV Guide on screen).
I am at my wits end - does anyone have a suggestion other than turning this thing into an anchor?