His lawyers are claiming that a girl tried to blackmail him a few years ago and this is related...
http://sportsillustrated.cnn.com/2012/basketball/nba/05/11/chris.andersen.spurned.fan.ap/index.html?sct=hp_t2_a9&eref=sihpGirl claims she's of age (specifically claims she is 21), sends scantily-clad images to Birdman, they are together for a while, he breaks off the relationship, her mom tries to make him pay for "everything on her Amazon wish list." Either she lied about her age and that is what they are investigating or she got pissed and filed a false claim of kiddie porn to make him look bad. That seems to be what his lawyers are saying.