Err you mean from ground loops?
Heh typically you are better off with a bus powered device for ground loop problems due to there only being one electrical ground in the system. However if you hook up external devices into the system through the sound card then it may be a moot point depending on how they get plugged in and how good the isolation is on the grounds, what the difference is in potential to ground between the various AC grounds they use.....
So what that all means is that anything in audio can really suffer from a gorund loop. However having a bus powered devices takes out one method in which it can happen, but there are other ways it can happen.