Amazing Position

This position is one that would have occured in a game between a friend of mine and an FM but my friend missed this continuation....but I cannot blame him. Fritz 6 and Rybka 2.2 also miss the winning line even after letting them think for a while. I was messing around analyzing his game and I found the winning continuation. Can anybody else find it?

This position occured after white played e4 and black responded with ...b4. What is the winning continuation?