I believe Guitar Rig is software not hardware. If I am correct then there is another piece of the puzzle... the interface to your machine. What is that piece...? What do you connect your guitar cable into on your computer...?
Personally I think that may be were the issue is... If you look at the configuration for the interface... do you have options like maybe ... use your interface as a sound card...? If so, you might try that setting and see if it helps.