???en_US.errors.required??? instead of fileds names

Hi,
I'm using the validator framework with struts, in order to validate the user data. And I wanted to get the error messages from the MessageResources_en.properties file. But instead it writes ???en_US.errors.required??? instead of fileds names

I don't think that there's a problem with my message resource file as the rest of the fields titles in the page are displayed properly from this property file

Here s my Form JSP
<html:form method="post" action="vfcLogin" onsubmit="return validateVFCLoginForm(this);">

<fmt:message key="my.pin" />
<html

assword styleClass="inputText" property="pin" redisplay="false"/>

<html:submit styleClass="okBtn" ><fmt:message key="button.submit"/></html:submit>

<html:errors/>

<html:javascript formName="VFCLoginForm"/>

and my validation.xml
<form name="VFCLoginForm">
<field property="pin"
depends="required">
<arg key="error.pin.required"/>
</field>
</form>

and in my struts-config.xml

<struts-config>
<form-beans>
<form-bean name="VFCLoginForm"
type="com.bean.VFCLoginForm" />
</form-beans>

<action-mappings>
<action path="/vfcLogin"
type="com.action.VFCLoginAction" name="VFCLoginForm"
scope="request" validate="true" input="/JSP/vfc.jsp">
<forward name="success" path="/JSP/vfc.jsp" />
</action>
</action-mappings>

<message-resources parameter="MessageResources" null="false" />

<plug-in className="org.apache.struts.tiles.TilesPlugin">
<set-property property="definitions-config"
value="/WEB-INF/tiles-defs.xml" />
<set-property property="moduleAware" value="true" />
<set-property property="definitions-parser-validate"
value="true" />
</plug-in>


<plug-in className="org.apache.struts.validator.ValidatorPlugIn">
<set-property property="pathnames"
value="/WEB-INF/validator-rules.xml,/WEB-INF/validation.xml" />
</plug-in>

</struts-config>

and defined the message resource property file in my web.xml

<context-param>
<param-name>javax.servlet.jsp.jstl.fmt.localizationContext</param-name>
<param-value>MessageResources</param-value>
</context-param>

So i really don't know where this error is coming from.
Any idea?

Another thing, how do I define whether do I want a popup msg to appear or just write the errors in the page?
currently this code is generating a popup msg with this error msg ???en_US.errors.required???

Hey all,
I found out what the problem is. It was in the validation.xml.
All you have to do is to replace
<arg key="error.pin.required"/>
with
<msg name="required" key="error.pin.required"/>

Didn't know the reason, perhaps it's a bug or something.

Any suggestions about how to specify whether I need it in popup msg or to be printed in the page?