Running the Download Resource example as a portlet causes this:
22:42:06,442 ERROR [jsp:52] java.lang.ClassCastException: com.icesoft.faces.webapp.http.portlet.InterceptingPortletSession
at org.icefaces.application.showcase.view.bean.examples.component.outputResource.OutputResourceBean.<init>(OutputResourceBean.java:59)
at java.lang.Class.newInstance0(Class.java:350)
at java.lang.Class.newInstance(Class.java:303)
at com.sun.faces.mgbean.BeanBuilder.newBeanInstance(BeanBuilder.java:186)
at com.sun.faces.mgbean.BeanBuilder.build(BeanBuilder.java:106)
at com.sun.faces.mgbean.BeanManager.createAndPush(BeanManager.java:368)
at com.sun.faces.mgbean.BeanManager.create(BeanManager.java:230)
at com.sun.faces.el.ManagedBeanELResolver.getValue(ManagedBeanELResolver.java:88)
at javax.el.CompositeELResolver.getValue(CompositeELResolver.java:53)
at com.sun.faces.el.FacesCompositeELResolver.getValue(FacesCompositeELResolver.java:72)
at org.apache.el.parser.AstIdentifier.getValue(AstIdentifier.java:61)
at org.apache.el.parser.AstValue.getValue(AstValue.java:103)
at org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:186)
at com.sun.faces.application.ValueBindingValueExpressionAdapter.getValue(ValueBindingValueExpressionAdapter.java:113)
at com.icesoft.faces.component.outputresource.OutputResource.getResource(OutputResource.java:66)
at com.icesoft.faces.component.outputresource.OutputResourceRenderer.encodeBegin(OutputResourceRenderer.java:24)
at javax.faces.component.UIComponentBase.encodeBegin(UIComponentBase.java:813)
at com.icesoft.faces.renderkit.dom_html_basic.DomBasicRenderer.encodeParentAndChildren(DomBasicRenderer.java:350)
at com.icesoft.faces.renderkit.dom_html_basic.GridRenderer.encodeChildren(GridRenderer.java:203)
at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:837)

The culprit is the constructor for the OutputResourceBean:

public OutputResourceBean(){
ServletContext context = ((HttpSession)FacesContext.getCurrentInstance().getExternalContext()
.getSession(false)).getServletContext();
try{
imgResource = new ByteArrayResource( toByteArray( new FileInputStream( new File( context.getRealPath("/WEB-INF/resource/logo.jpg")))));
pdfResource = new FileResource( new File(context.getRealPath("/WEB-INF/resource/WP_Security_Whitepaper.pdf")));
pdfResourceDynFileName = new FileResource( new File(context.getRealPath("/WEB-INF/resource/WP_Security_Whitepaper.pdf")));
}
catch(Exception e){
e.printStackTrace();
}
}

It tries to create these resources based on real file locations using ServletContext.getRealPath(). Using the Servlet API directly in this way makes it unsuitable for working as a portlet. PortletContext has a matching API so that would be one option to fix it. A better solution would be to do the straight JSF thing and use one of the ExternalContext.getResource* methods (getResource, getResourceAsStream, or getResourcePaths) and avoid having to check for which environment it's running in.

I'm commenting out this portlet for the 1.7.2 release and will mark it as being re-introduced into the 1.8 release.