I'm having a similar problem as well. I am deploying a WAR to JBoss 3.2 which has packaged the O'Reilly servlet library as part of the web application. A co-worker has also deployed the O'Reilly library as well as in a separate WAR (under /WEB-INF/classes/). Well, my application is using the MultiPartRequest class from her application versus my own. This is causing problems as she has modified her MultiPartRequest to use a class which is not registered in a classpath for myself.
What is the solution or explanation as to why JBoss is not allowing my application to use its own packaged libraries, and is sharing another from a separate app.
Correction: I'm running JBoss v.4.0.1
You both are having classloader issues. See this http://www.jboss.org/wiki/Wiki.jsp?page=JBossClassLoadingUseCases
You can work around this by disabling the "UseJBossWebLoader" in the jbossweb-tomcat50.sar/META-INF/jboss-service.xml file.
Best to read up on the JBoss UCL to get a handle on why this happens.