With JSP2.1 the "#" character is used in the JSP EL. OGNL does use this escape character as well.
To get around this there is the possibility to disable JSP EL in web.xml:

<jsp-config>
  <jsp-property-group>
    <url-pattern>*.jspx</url-pattern>
    <el-ignored>true</el-ignored>
  </jsp-property-group>
</jsp-config>    

related threads:

• http://www.mail-archive.com/user%40struts.apache.org/msg56749.html
• http://forums.opensymphony.com/thread.jspa?messageID=100059