My guess proved correct: Air America's check bounced. According to the Chicago Tribune (registration required):

Arthur Liu, owner of Multicultural Radio Broadcasting, which owns Air America affiliates WNTD-950 AM in Chicago and KBLA-1580 AM in Los Angeles, said Air America bounced a check and owes him more than $1 million.

You'll recall the massive, breathless media coverage Air America's debut received two weeks ago. So far, I've checked the websites for CNN, MSNBC, ABC, and even FOX News, and can't find a single thing on any of their front pages about the network losing two of its three largest markets, or about it evidently not having enough operating capital for its first month of operations. Go figure.