When I have had the few problems with my TomTom, I just call them. They answer quickly and have resolved the issue. Have you tried that?
This seems to be a common problem with your model.
TomTom suggest that you do four things before updating.
1. Make sure your screen saving is disabled.
2. Make sure your computer doesn't go into sleep mode or hibernation.
3. Turn off your antivirus.
4. Turn off your firewall.
No 1 is very important.
No 2 is very important.
No 3 is usually important. It will enable itself after a reboot.
No 4 can be important and again it will be enabled after a reboot.