The jmx-console, or the normal tomcat status pages are broken, probably due to the tomcat6 upgrade.

E.g. accessing the jmx-console:
2006-07-05 14:10:18,350 ERROR [org.apache.catalina.core.ContainerBase.[jboss.web].[localhost].[/jmx-console].[jsp]] Servlet.service() for servlet jsp threw exception
java.lang.NoClassDefFoundError: org/apache/commons/el/ExpressionEvaluatorImpl
at org.apache.jasper.compiler.JspUtil.<clinit>(JspUtil.java:61)
at org.apache.jasper.JspCompilationContext.getServletClassName(JspCompilationContext.java:334)
at org.apache.jasper.JspCompilationContext.getClassFileName(JspCompilationContext.java:484)
at org.apache.jasper.compiler.Compiler.isOutDated(Compiler.java:379)
at org.apache.jasper.compiler.Compiler.isOutDated(Compiler.java:332)
at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:560)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:303)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:174)
at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:74)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:222)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:823)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:606)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:444)
at java.lang.Thread.run(Thread.java:595)

Accessing the tomcat status page:
2006-07-05 14:13:44,356 ERROR [org.apache.catalina.core.ContainerBase.[jboss.web].[localhost].[/].[Status Servlet]] Servlet.service() for servlet Status Servlet threw exception
javax.management.AttributeNotFoundException: Cannot find attribute minSpareThreads
at org.apache.tomcat.util.modeler.BaseModelMBean.getAttribute(BaseModelMBean.java:259)
at org.jboss.mx.server.RawDynamicInvoker.getAttribute(RawDynamicInvoker.java:117)
at org.jboss.mx.server.MBeanServerImpl.getAttribute(MBeanServerImpl.java:565)
at org.apache.catalina.manager.StatusTransformer.writeConnectorState(StatusTransformer.java:250)
at org.jboss.web.tomcat.tc6.StatusServlet.doGet(StatusServlet.java:255)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:174)
at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:74)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:222)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:823)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:606)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:444)
at java.lang.Thread.run(Thread.java:595)