Tomcat error

[Marcellus Tryk]

Hi all -
When I attempted to restart Tomcat to pick up a new web application, Tomcat fails with the following error:

 
ERROR reading /var/tomcat4/conf/server.xml
At Line 18 /Server/Listener/ 
className=org.apache.catalina.mbeans.ServerLifecycleListener debug=0 

Catalina.start: java.lang.ClassNotFoundException: 
org.apache.catalina.mbeans.ServerLifecycleListener
java.lang.ClassNotFoundException: 
org.apache.catalina.mbeans.ServerLifecycleListener
        at org.apache.catalina.loader.StandardClassLoader.loadClass
 

The only things I've done since the last time it was restarted was add a war file to the webapps directory and a jar file to the common/lib directory. I've undone these but still no go. Any hints?
Thanks,
Mars