java.lang.NoClassDefFoundError: weblogic/kernel/KernelStatus

This saved my life:

http://blogs.oracle.com/jamesbayer/2008/08/workshop_for_weblogic_103_jee.html

In the classpath tab, be sure to add the wlclient.jar file located here \wlserver_10.3\server\lib to the User Entries section and remove the WebLogic System Libraries from the Bootstrap Entries section.  If you forget to remove the WebLogic System Libraries, you will get a stack like this: Exception in thread "Main Thread" java.lang.NoClassDefFoundError: weblogic/kernel/KernelStatus