求解！使用Acegi的系统在WebSphere5.0上部署遇到的问题

我在系统上第一次使用了Acegi控制用户的权限，在Tomcat5.0上开发调试一切正常，可是部署到WebSphere5.0上出现了错误-----〉
[06-8-18 15:07:37:793 CST] 41213509 WebGroup      E SRVE0026E: ［Servlet 错误］－［FormLoginServlet］：com.ibm.ws.webcontainer.servlet.exception.ServletNotFoundException: 未找到 Servlet：FormLoginServlet
at com.ibm.ws.webcontainer.webapp.WebAppServletManager.getServletReference(WebAppServletManager.java:458)
at com.ibm.ws.webcontainer.webapp.WebApp.getServletReference(WebApp.java:652)
at com.ibm.ws.webcontainer.webapp.WebAppRequestDispatcherInfo.calculateInfo(WebAppRequestDispatcherInfo.java:139)
at com.ibm.ws.webcontainer.webapp.WebAppRequestDispatcherInfo.<init>(WebAppRequestDispatcherInfo.java:59)
at com.ibm.ws.webcontainer.webapp.WebApp.getRequestDispatcher(WebApp.java:1462)
at com.ibm.ws.webcontainer.webapp.WebApp.getRequestDispatcher(WebApp.java:1421)
at com.ibm.ws.webcontainer.srt.WebAppInvoker.handleInvocationHook(WebAppInvoker.java:268)
at com.ibm.ws.webcontainer.cache.invocation.CachedInvocation.handleInvocation(CachedInvocation.java:71)
at com.ibm.ws.webcontainer.srp.ServletRequestProcessor.dispatchByURI(ServletRequestProcessor.java:182)
at com.ibm.ws.webcontainer.oselistener.OSEListenerDispatcher.service(OSEListener.java:334)
at com.ibm.ws.webcontainer.http.HttpConnection.handleRequest(HttpConnection.java:56)
at com.ibm.ws.http.HttpConnection.readAndHandleRequest(HttpConnection.java:618)
at com.ibm.ws.http.HttpConnection.run(HttpConnection.java:439)
at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:593)
这是怎么回事啊？