I am not sure about which classloader ear/lib/common.jar belongs to. Try doing a
System.out.println(this.getClass().getClassLoader());
System.out.println(Thread.currentThread().getContextClassLoader());
in some classes from your common.jar and ejb.jar to make sure they are the same. If they are not, try logging the parent classloaders.
My guess is that the problem is that the common.jar classes cannot see the annotations or something like that.