Not that I am an arborist by any stretch but I had a similar problem with a couple of my maples and it was something called anthracnose. They good news is that will ugly for a year the tree doesnt die.
UNH has a great program where for $15 they will diagnose the problem and give you suggestions as needed.
check out
http://extension.unh.edu/Agric/AGPDTS/PlantH.htm
Good Luck!