Erro Class loader

alguem ja viu esse erro? estou usando websphere e plugin do tomcat

Bootstrap: Class loader creation threw exception
java.lang.RuntimeException: Unable to create the MBean server instance. Class org.jboss.mx.server.MBeanServerImpl has raised an exception in constructor: java.lang.NoClassDefFoundError: EDU/oswego/cs/dl/util/concurrent/ConcurrentReaderHashMap
at javax.management.MBeanServerFactory.createMBeanServer(MBeanServerFactory.java:180)
at javax.management.MBeanServerFactory.createMBeanServer(MBeanServerFactory.java:80)
at javax.management.MBeanServerFactory.createMBeanServer(MBeanServerFactory.java:74)
at org.apache.catalina.startup.Bootstrap.createClassLoader(Bootstrap.java:172)
at org.apache.catalina.startup.Bootstrap.initClassLoaders(Bootstrap.java:104)
at org.apache.catalina.startup.Bootstrap.init(Bootstrap.java:196)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:402)

Acho que está faltando essa classe aí!