According to the lawsuit, Douglas Green claims he had an agreement with Madsen to star in the movie "Vigilante" -- and paid him a cool $20k. But when production got delayed, Green claims Madsen tried to milk him for an additional $20k.
Green says he refused and Madsen never did the movie. He's suing Madsen for breach of contract and asking for his money back -- and more than $100,000 in damages.
A rep for Madsen tells TMZ he plans on filing a counter-suit, claiming he was never paid the balance of the money owed him after the initial $20k.