Hi jmc--
the first thing I would do is check with your local court clerk's office to make sure that they even filed a case in court against you. It is fairly common practice for collectors to use this tactic to scare people into paying immediately, before they have a chance to learn their rights. It is illegal to do so, but it still happens.
You said that the debt was past the SOL--but it isnt, because no matter how old it is, in most states if you make a payment on it, the clock restarts. So it is no longer outside the SOL unless the last payment you made was long enough back.
Also, they cannot put you in jail for most things regarding debts, but you can be found in contempt of court for some things if a case is ongoing in court. Again, check with the court clerk's office there--they cannot provide legal advice but they can often help you sort out what should be done as far as the proper procedures and so on. i would check with the court that the debt collector claims to have filed suit against you in before making any moves with the collector, just to be safe. I would most definitely not provide them with one shred of information until you can verify everything they are telling you as true.
One more thing--what do you mean when you say they "put a judgment against you"? Did you get served a summons and all that? Or did they just tell you that they put a judgment against you? If they did not actually sue you, then they cannot have a judgment against you. Some more info there can maybe help us to get you better information to help you out. Please get back to us.