Cannot call a method in an action class in portlet mode

I am not able to call a method in an action class when put in the portlet environment. In the web based environment its working fine. Can you help me in solving this issue. Here also I am pasting the code used for submitting the form.

<s:url id="url" action="TaskSearch" method="searchTask" namespace="/ems"/>

<s:a href="%

">
<img src="<s:url value="/FelixEms/images/search2.gif"/>" border="none"/></s:a>