急求struts问题解决方法

写了一个很简单的struts应用,问题是严重:   Error   loading   WebappClassLoader
    delegate:   false
    repositories:
        /WEB-INF/classes/
---------->   Parent   Classloader:
org.apache.catalina.loader.StandardClassLoader@1b9ce4b
  org.apache.struts.action.ActionServlet
java.lang.ClassNotFoundException:   org.apache.struts.action.ActionServlet
说找不到ActionServlet,struts.jar包已经导入了,先前写了一个是可以的....
web.xml配置
<web-app>
<servlet>
<servlet-name> action </servlet-name>
<servlet-class> org.apache.struts.action.ActionServlet </servlet-class>
<init-param>
<param-name> config </param-name>
<param-value> /WEB-INF/struts-config.xml </param-value>
</init-param>
<load-on-startup> 1 </load-on-startup>
</servlet>

<servlet-mapping>
<servlet-name> action </servlet-name>
<url-pattern> *.do </url-pattern>
</servlet-mapping>
struts-config配置:
<struts-config>      
<action-mappings>
<action   path= "/login "   type= "poson.action.login.StaffLoginAction "   scope= "request "   >
<forward   name= "failure "   path= "/error.jsp "/>
<forward   name= "success "   path= "/frame/main.jsp "/>
<forward   name= "modify "   path= "/sys_admin/right/staff/selfInfo_Modify.jsp "/>
</action>
</action-mappings>
</struts-config>
index.jsp中调用:
<form   name= "staffLoginForm "   method= "post "   action= "/login.do "   onSubmit= "return   checkLogin(); ">
感觉没有错,怎么搞的?

和你有一样的问题。怎么待高人指点。