###GolfScript, 80 Characters###

    .(65-.0<1$25>|\32-.0<\25>|&\.""=\"."=|!|!\([{)..31&26-!26*-}25*;]n+\"."=n" "if**

Most of the code is testing for valid input and the "print nothing"-option. The actual logic is 37 characters only.

[Test cases online](http://golfscript.apphb.com/?c=OydjJwouKDY1LS4wPDEkMjU%2BfFwzMi0uMDxcMjU%2BfCZcLiIiPVwiLiI9fCF8IVwoW3spLi4zMSYyNi0hMjYqLX0yNSo7XW4rXCIuIj1uIiAiaWYqKgpwdXRzCgo7J0guJwouKDY1LS4wPDEkMjU%2BfFwzMi0uMDxcMjU%2BfCZcLiIiPVwiLiI9fCF8IVwoW3spLi4zMSYyNi0hMjYqLX0yNSo7XW4rXCIuIj1uIiAiaWYqKgpwdXRzCgo7J0AnCi4oNjUtLjA8MSQyNT58XDMyLS4wPFwyNT58JlwuIiI9XCIuIj18IXwhXChbeykuLjMxJjI2LSEyNiotfTI1KjtdbitcIi4iPW4iICJpZioqCnB1dHMKCgoKCg%3D%3D)