if you have wl11 ejb server and in that environment generated ejb client and deploy to wl12 it will give you this exception
java.lang.NoSuchMethodError: weblogic.rmi.internal.MethodDescriptor.(Ljava/lang/reflect/Method;Ljava/lang/Class;ZZZZII)V
so there are some solutions like this. but what I did was different. I deleted *******_WLStub.class from client jar and deployed the ear that way so at the end wl12 generates it on the fly just like jsp first compilation. and it works.