It took them forever to do it, but they did finally end up paying me, after the first delinquent check they sent me bounced and caused my bank to charge me the fee - they paid for that as well. I did a promotional gig for them again in November of 2009, so it's anyone's guess as to when I'll get the $400 I'm due for that.
My advice: only do work for them if you don't need the money up front. I even told the client I was working for as well as a couple other potential clients that they make working for them really difficult, but it's nice when you get that random check you're due.
When all else fails, do what I did: talk to someone with legal advice in San Diego (where they're headquartered). I got passed around within the city, but ended up talking to someone with good information about filing claim against The Agency. When I discussed that option with Ms. Kelly Miller at the time, she snapped to it.
Hope this helps.