when we swith webs very quickly ,it will occur the error,we don't know whether it is a problem of jboss configuration or something else. The error is as follows:

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.compiere.model.MTab.toString(MTab.java:2282)
java.lang.String.valueOf(String.java:2577)
java.lang.StringBuilder.append(StringBuilder.java:116)
org.compiere.www.WWindowStatus.toString(WWindowStatus.java:75)
org.compiere.util.WebEnv.getServletInfo(WebEnv.java:659)
org.compiere.util.WebEnv.addFooter(WebEnv.java:490)
org.compiere.util.WebUtil.createResponse(WebUtil.java:485)
org.compiere.util.WebUtil.createErrorPage(WebUtil.java:109)
org.compiere.www.WWindow.doGet(WWindow.java:143)
javax.servlet.http.HttpServlet.service(HttpServlet.java:697)
javax.servlet.http.HttpServlet.service(HttpServlet.java:810)
org.compiere.www.WFilter.doFilter(WFilter.java:142)
org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:81)
note The full stack trace of the root cause is available in the Apache Tomcat/5.5.9 logs.

Apache Tomcat/5.5.9