Ex asking for money after settlement

[zurra]

Ex-husband and I had discussions about how to divide property in March 2006, and discussed whether we'd split our apartment deposit. We signed a settlement agreement May 2006 that did not include the deposit (and didn't include much of anything specific), but the judgment states it is a final settlement. He asked for this apartment deposit at a hearing in January and my attorney explained to his that he cannot go back and renegotiate the property settlement, so I thought he'd dropped it. Now he is threatening to sue me in small claims court and trying to get me to go to a $100 per hour mediator to discuss a $900 apartment deposit. I believe his claim is totally invalid--am I right? And is there anything I can do to prevent his constant harassment and threats of frivolous lawsuits? He has legal insurance and doesn't pay for his attorney so he doesn't care how often he goes to court and is constantly threatening to go back even right after we've reached an agreement.