You are correct in that others have reported that "Fix it" from within OneCare when a problem has been detected does not work. We don't know the cause. The Fix it button calls a script that is part of the Help System and executes a series of programmed steps to repair a problem. I suspect that something is blocking the scripted action, perhaps IE security settings, or the code that needs to be executed is broken on your PC. As Jim noted, the best thing to do is to contact OneCare support per the instructions at the link he provided.
-steve