SEVERE: Exception sending context destroyed event to listener instance of class org.apache.myfaces.webapp.StartupServletContextListener

Erro:

SEVERE: Exception sending context destroyed event to listener instance of class org.apache.myfaces.webapp.StartupServletContextListener
java.lang.LinkageError: loader constraint violation: loader (instance of org/apache/catalina/loader/WebappClassLoader) previously initiated loading for a different type with name "javax/el/ExpressionFactory"
   at java.lang.ClassLoader.defineClass1(Native Method)
   at java.lang.ClassLoader.defineClass(ClassLoader.java:620)
   at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)

Solução: Existe uma classe, provavelmente as que controlam a integracao das expressoes de linguagem com as expressoes de ligacao duplicadas. ocorre quando utiliza .jar's destas classes no tomcat 6 que já possui esta integracao