Where did you include this jar file? Which folder? Do a quick search to see if a jar file with this exact same name is anywhere else on your classpath. Open up the jar file with WinZip and check to see if that actual file is in the jar.
I believe there are different versions of this file floating around.
I've downloaded the last version of Hibernate distributive and placed all the libraries from lib/required directory in the classpath of my webApp. Do i need any additional libraries in order to get app work?
If you think you've done too much, usually it means you've done too few.