Well, on the one hand, the robots.txt checker says it only checks for msnbot -- but on the other hand, I would suggest it report something less confrontational as "invalid user-agent."
I would suggest "User-Agent Not Recognized by MSNBot. Associated commands ignored." Or perhaps the portions of the robot.txt file in the textarea that would be ignored by the msnbot could be grayed out meaning that msnbot is not looking in those spots for direction.