proguard errors

Note: there were 1 unresolved dynamic references to classes or interfaces.
      You should check if you need to specify additional program jars.
Note: there were 2 class casts of dynamically created class instances.
      You might consider explicitly keeping the mentioned classes and/or
      their implementations (using '-keep').
Warning: there were 2 unresolved references to classes or interfaces.
         You may need to specify additional library jars (using '-libraryjars'),
         or perhaps the '-dontskipnonpubliclibraryclasses' option.
java.io.IOException: Please correct the above warnings first.
	at proguard.Initializer.execute(Initializer.java:308)
	at proguard.ProGuard.initialize(ProGuard.java:210)
	at proguard.ProGuard.execute(ProGuard.java:85)
	at proguard.ProGuard.main(ProGuard.java:499)