If it isn't connected to the PC does it actually work or is it freezing even then?
I had an issue with my old Go510 when I did a firmware update. At first it refused to play the game. However it was still talking to the PC, though not very obviously.
In TomTom Home there is an option to remote control the sat nav from the PC. It may or may not work but what I had to do was remote control the device with home, browse the map for a minute or two anything like that. Then switch it off and back on again and it all started working fine again.
Mind you if it won't even talk to home when connected to the PC you may be in trouble. If you are really unlucky you may have to deal with TomTom Customer Support to get it fixed. Good luck with that