It appears that the issue is that Eclipse will rebuild and redeploy the EAR to JBoss while at the same time opening up IE and trying to load the JSP. JBoss eventually will see the new EAR and it has to go through a process of unloading the current EAR from memory and then reloading the new EAR. The error you see is happening when JBoss unloads the current EAR from memory as far as I can tell(?). I submitted this question to the installation, configuration forum but got no response. Then I read I was to suppose to submit here first since I'm a newbie. I just installed JBoss on my local machine but when trying to "run on server" a JSP page from within Eclipse 3.2 IDE I am getting the following error: | HTTP Status 500 - | | type Exception report | message | description The server encountered an internal error () that prevented it from fulfilling this request. | exception | java.lang.NullPointerException | org.jboss.mx.loading.RepositoryClassLoader.findClass(RepositoryClassLoader.java:620) | java.lang.ClassLoader.loadClass(Unknown Source) | org.jboss.mx.loading.RepositoryClassLoader.loadClassImpl(RepositoryClassLoader.java:464) | org.jboss.mx.loading.RepositoryClassLoader.loadClass(RepositoryClassLoader.java:405) | java.lang.ClassLoader.loadClass(Unknown Source) | java.lang.ClassLoader.loadClassInternal(Unknown Source) | org.acegisecurity.ui.ntlm.NtlmProcessingFilter.onPreAuthentication(NtlmProcessingFilter.java:344) | org.acegisecurity.ui.AbstractProcessingFilter.doFilter(AbstractProcessingFilter.java:200) | org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:274) | org.acegisecurity.ui.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:110) | org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:274) | org.acegisecurity.context.HttpSessionContextIntegrationFilter.doFilter(HttpSessionContextIntegrationFilter.java:191) | | org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:274) | org.acegisecurity.util.FilterChainProxy.doFilter(FilterChainProxy.java:148) | org.acegisecurity.util.FilterToBeanProxy.doFilter(FilterToBeanProxy.java:90) | org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96) | note The full stack trace of the root cause is available in the Apache Tomcat/5.5.20 logs. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3981746#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...