I was walking in my neighborhood and one of my neighbors was walking his dog on a leash. I went up to talk with the neighbor and while we were talking the unprovoked dog bit me and took off a chunk out ofmy leg? Do I have a case?

It depends.  Even though your neighbor was following the leash law, he/she may have had a duty to warn you of his dog's propensity to bite.  If the dog had a history of biting or aggressive behavior that would have put the owner on notice of its vicious propensity, there may be a case.  The knowledge question runs both ways as well.  If you were aware of the danger of the dog potentially biting you, there may be an assumption of the risk argument made against you.