I've found myself in a bad situation with a studio I did some freelance work for. Swamp Ape Studios, owned by O'Neal Pignani who also goes by the name Von Kreep on facebook and I'm assuming that's a pseudonym he uses on his artwork. He seems to prey on students and artists fresh out of school looking for their first jobs and artists who are desperate for work. He will contact you with projects his studio is looking to hire artists for, these are real projects with real budgets, but when the time comes for him to pay artists he somehow "just can't afford to pay you right now". I am unfortunately dealing with this right now, and doing what I can to keep him from pulling this on more artists. Mine is the second project that I've heard O'Neal pull this scam with, I only heard of the first a week or so before completing the one I was working on.. As far as I know his studio has never paid any of their artists, they just move on and find new ones.
Avoid this studio.

Don't mean to preach but this is a lesson learned for me. Make sure you have a Written Contract and Get a percent up front, unless you personally know this new employer, or is a well known and established person (in which case they will probably already have a contract ready), don't accept payment on delivery for freelance work especially without a contract.
Its easy to glaze over these things when you're just interested in getting to work, and I'm a bit embarrassed to admit that I neglected to take these important steps before starting this project.

^^^ Sounds like 'Von Kreep' is a scumbag.

I hope you withheld the finished artwork files and only sent him compressed proofs.

. . . and/or pissed through his letterbox!

Actually I'm on my way to do that right now!

Moog, unfortunately not.. He had us all fleeced, and us getting paid was dependent on us delivering a completed episode.. Since there are so many steps between animation and complete he got all of our finished work..