I got two almost identical Struts-Applications.
After some hot-deployments (touch web.xml is enough) I get an exception:

2005-02-09 15:16:47,711 ERROR [org.jboss.web.localhost.Engine] ----- Root Cause -----
java.lang.NoClassDefFoundError: java/util/Iterator
at org.apache.struts.action.ActionServlet.destroyModules(ActionServlet.java:476)
at org.apache.struts.action.ActionServlet.destroy(ActionServlet.java:286)
at org.apache.catalina.core.StandardWrapper.unload(StandardWrapper.java:1269)
at org.apache.catalina.core.StandardWrapper.stop(StandardWrapper.java:1594)
at org.apache.catalina.core.ContainerBase.removeChild(ContainerBase.java:952)
at org.apache.catalina.core.StandardContext.removeChild(StandardContext.java:3152)
[..]

This error does not happen if I set 'UseJBossWebLoader' to 'false' in 'deploy/jbossweb-tomcat50.sar/META-INF/jboss-service.xml'.

The web-applications are really simple, they just consists of the following files:
web.war/META-INF/MANIFEST.MF
web.war/WEB-INF/conf/struts-config.xml
web.war/WEB-INF/lib/struts.jar
web.war/WEB-INF/web.xml
ipcare.war/META-INF/MANIFEST.MF
ipcare.war/WEB-INF/conf/struts-config.xml
ipcare.war/WEB-INF/lib/struts.jar
ipcare.war/WEB-INF/web.xml

To produce the problem I just did

> while true
> do
> touch web.war/WEB-INF/web.xml
> sleep 5
> touch ipcare.war/WEB-INF/web.xml
> sleep 5
> done

It seems that the UnifiedClassLoad has some problems. After 15 h of searching I'm giving up.