I downloaded Jetspeed 2 and ran it using startup.bat. I surfed to http://localhost:8080/jetspeed/portal/ and the page loaded though tomcat made a mess of exceptions. pasted below. I Also noticed that the 'Login Portlet' was not available on the home page. "Portlet is Not Available: j2-admin::LoginPortlet Reason: null".
OK, the Jetspeed 2 requirements state that Servlet API 2.4 (and thus TC 5) is sufficient. But still, that class is part of JSP 2.1 which is not supported by TC 5. Since the exception is apparently thrown from inside a JSTL tag, are you by any chance using JSTL 1.2 (which relies on JSP 2.1)?