For those of you who are using the new NCover 2 on Vista there is something you need to be aware of. The installer runs the registration wizard at the end of the installation but does not run it elevated. The wizard accepts your key and gives you a successful registration message but any attempt to run any of the binaries will fail with a 'not registered' message.
To solve this, just run the NCover registration wizard as administrator. All components of NCover should work once this is done.