Most likely issue is the USB cable - they're ridiculously easily damaged but are at least cheap to replace (around $1 on ebay).
If that's not it then it's either the USB port on the tablet (since you seem to think the issue is at that end) or drivers on the PC.
You could try turning the tablet off and gently cleaning the USB port - if that doesn't work then it's a repair job, I'm afraid.
Before sending the tablet for repair, it's probably worth trying a re-install of the drivers on the PC, though:
- disconnect the tablet from the PC
- uninstall all drivers and tablet-related software (e.g. Keis) from the PC
- restart the PC and the tablet
If your tablet came with PC software like Kies (Keis?) or HTC Sync, install that. NB: do NOT connect the tablet until prompted.
If your tablet didn't come with PC software, connect it to the PC.
In both cases DO NOT remove the tablet until all the drivers have successfully installed.
