I starting getting the "Error C5, HID Not Found" error when trying to download to a remote. The Pronto was the only HID device installed in device manager, so there was no conflicting device to uninstall (the error is usually due to a Logitech keyboard or similar device causing interference.)

The only way to get it working again was to reinstall ProntoEdit Pro.

EDIT: Running ProntoEdit Pro as Admin seems to have fixed the "Error C5 HID" problem without the need to continually reinstall.