When he charged back, paypal should have sent you an email allowing you to give your side of the story.
This happened to me when I sold something on eBay, the guy got it and said that it wasn't working when it was in full working order when I sent it, and the guy didn't pay for postal insurance. He issued a chargeback and my paypal was in -$200.
Paypal contacted me and I gave my side of the story, about a month or so later they emailed me back saying that they had found me to be the honest party in the transaction and so my paypal account was no longer in -.
The reason why your paypal is in -xxx is because they are still looking into the matter.
Have you given your side of the story?
If not login to your paypal account and click on 'Resolution Centre'
You should be able to look through the claim/chargeback there and if you havn't done so already, provide your argument.
Hope this helps