Alguem saberia me dizer???

Fala galera!!!Estou tentando rodar um projeto java, e está aparecendo o seguinte erro:Activation.main: an exception occurred: log recover failed with exception: java.lang.ClassCastException: cannot assign instance of java.util.HashMap to field sun.rmi.server.Activation.groupTable of type java.util.Hashtable in instance of sun.rmi.server.Activationjava.io.IOException: log recover failed with exception: java.lang.ClassCastException: cannot assign instance of java.util.HashMap to field sun.rmi.server.Activation.groupTable of type java.util.Hashtable in instance of sun.rmi.server.Activation at sun.rmi.log.ReliableLog.recover(Unknown Source) at sun.rmi.server.Activation.startActivation(Unknown Source) at sun.rmi.server.Activation.main(Unknown Source)Se alguem souber o que significa e como resolvo tal problema, favor me digam.Abraços.