When you scan, does your PVR offer you the choice of 'adding' or 'replacing' channels? If so (and assuming that you previously selected 'add'), scan again and select 'replace' (or 'New scan' or however else your set labels a completely fresh set up). Otherwise, for example, your PVR might still think that Film 4 is on Channel 32. (It should now appear on Channel 15).
Other than that, I can only suggest disconnecting your PVR from the mains, waiting a minute or two, then re-connecting it. (That might sound very crude but it's amazing how often it fixes problems with digiboxes!).
Chris