I've gotten some weird plumbob bugs as well since installing NL. My avatar shows the results of one of them. They have always cleared up on their own though after exting and going back to the lot.
Your son can try this:
http://www.moreawesomethanyou.com/smf/index.php?topic=1186.0It might or might not help get the sim to move out. If that fails, he should be able to evict the sim from the neighborhood screen and move them that way.
Edit to the Edit: Well okay, then. The skillbar should go away once he gets the sim to move. That should reset everything.