解决办法:

修改 web.xml 中 DWR 配置信息或者换tomcat6.0就不会有此问题了！

原:

<servlet> 
      <servlet-name>dwr-invoker</servlet-name> 
     <servlet-class>org.directwebremoting.spring.DwrSpringServlet</servlet-class> 
     <init-param>
      <param-name>debug</param-name>
      <param-value>true</param-value>
  </init-param>
</servlet>

加入跨域调用配置信息，修改为:

<servlet> 
      <servlet-name>dwr-invoker</servlet-name> 
      <servlet-class>org.directwebremoting.spring.DwrSpringServlet</servlet-class> 
      <init-param>
             <param-name>debug</param-name>
             <param-value>true</param-value>
      </init-param>
      <init-param>
             <param-name>crossDomainSessionSecurity</param-name>
             <param-value>false</param-value>
      </init-param>
      <!--<init-param>
            <param-name>allowScriptTagRemoting</param-name>
            <param-value>true</param-value>
      </init-param>--><!--此处默认为true可以不加-->

如果采用与Spring整合方式
修改dwr.xml文件为：

<dwr:controller id="dwrController" debug="true" >
    <dwr:config-param name="crossDomainSessionSecurity" value="false" />
    <dwr:config-param name="allowScriptTagRemoting" value="true" />
    <dwr:config-param name="debug" value="true" />
</dwr:controller>