I definitely recommend that you reinstall from Steinberg files. Make sure your product is registered in your MySteinberg account. If that is all set, hopefully a download for Cubase 6 will be available there. If not, I’m sure they would give you a link to download it if your product is registered. You can read about activation and reactivation here but, since the CB 6 license is on a USB dongle, your move should be pretty easy.
Regards 