Same behavior in the showcase. Details below:

 ice:gMap > Render Type

Navigating to the render type page displays Server Internal Error popup. (only reproducible in IE9 with document mode set to IE9, works fine in IE8, IE7, Chrome and FF. Also works in IE9 mode with document mode of IE8 or 7).
Console output for IE9 & document mode set to IE9:
[window] received error message [code: 200]: <?xml version='1.0' encoding='UTF-8'?>
<partial-response><error><error-name>class java.lang.NullPointerException</error-name><error-message><![CDATA[]]></error-message></error><changes><extension aceCallbackParam="validationFailed">{"validationFailed":false}</extension></changes></partial-response>

Related JIRA - ICE-7704
uncomment
//@MenuLink(title = "menu.compat.map.subMenu.type", exampleBeanName = MapType.BEAN_NAME),
in org.icefaces.samples.showcase.example.compat.map.MapBean and launch app in IE9 to reproduce.

NOTE: The showcase application was deployed on Tomcat 7 during the test. It was using the icefaces 3 trunk code (rev#27509). Visually you will be able to see a Server Internal Error popup when navigating to ice:gMap - Render Type example.