Do a system reset and give it 24 hours. If its just a HD or standard receiver unplug it for 15-20 sec and then plug it back in. If its a TiVo then use the menus and 'Reset Recorder'.
The upgrade should download the next time its scheduled, which is generally ~2am. If the TV is on you'll get the option to get the upgrade later, otherwise next time you sit down to watch TV it will generally let you know that it happened.
If the above doesn't work, there's probably not a whole lot DTV can do.