A weird problem solved on Sun Access Manager

Symptom: Only can access login module once, will get following error when trying to access login module at the second time.

Error:
[22/May/2009:18:08:25] failure ( 8127): for host 149.171.129.78 trying to GET /amserver/UI/Login, service-j2ee reports: StandardWrapperValve[

LoginServlet]: PWC1406: Servlet.service() for servlet LoginServlet threw exception
java.lang.IncompatibleClassChangeError
at com.sun.identity.authentication.UI.LoginViewBean.forwardTo(LoginViewBean.java:328)
at com.iplanet.jato.ApplicationServletBase.dispatchRequest(ApplicationServletBase.java:981)
at com.iplanet.jato.ApplicationServletBase.processRequest(ApplicationServletBase.java:615)
at com.iplanet.jato.ApplicationServletBase.doGet(ApplicationServletBase.java:459)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:796)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:917)
at org.apache.catalina.core.ApplicationFilterChain.servletService(ApplicationFilterChain.java:398)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:185)
at com.sun.identity.setup.AMSetupFilter.doFilter(AMSetupFilter.java:86)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:217)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:185)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:275)
at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:255)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:188)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:586)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:556)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:187)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:586)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:556)
at com.sun.webserver.connector.nsapi.NSAPIProcessor.service(NSAPIProcessor.java:160)

Reason:
mismatch of Sun Access Manager version and amserver web application version

Solution:
replace am_auth_ui.jar, am_mfwkexc.jar, jato.jar under /var/opt/SUNWwbsvr7/https-am/web-app/am/amserver/WEB-INF/lib
using the jars in amserver.war under /opt/SUNWam