See an earlier question on Proguard errors with unity-classes.jar.
This is an issue with the classes in the Unity library: some of the preverification metadata are corrupt. You should check if there is a more recent version. Otherwise, you could modify ProGuard to accept the corrupt classes, as discussed on its issue tracker.
Note that you should not add -libraryjars or -injars to your configuration. The Android build process (Ant, Eclipse, Gradle) already specifies those options for you.