Re: Any lawyers here? If so, I have a question.
Gong from 10 to 0 would make you have more withheld, so you should be getting more back - maybe it was the other way around?
Secondly, the fact you owe money now means you paid in less to the system during the year. You didn't "lose" anything. So I'm not sure what you would sue for.
EDIT: Misread the first part so I retract my first thing. But not my second :-)