I am using JBoss 4.0.5, Ajax4jsf 1.1.1 with myfaces 1.5 and tomahawk 1.7.
Add <a4j:support> to <t:selectOneMenu>, the following is the response(I removed those matched XML elements).
<?xml version="1.0"?> <html lang="en" xmlns="http://www.w3.org/1999/xhtml"><body><span id="ajax-update-ids"><input type="hidden" name="jsf_sequence" value="3" /><input type="hidden" name="javax.faces.ViewState" id="javax.faces.ViewState" value="rO0ABXVyABNbTGphdmEubGFuZy5PYmplY3Q7kM5YnxBzKWwCAAB4cAAAAAN0AAEzcHQACS9zZGFkLmpzcA==" /></span><meta id="Ajax-Response" name="Ajax-Response" content="true" /><!-- MYFACES JAVASCRIPT --> <script type="text/javascript">//<![CDATA[ function getScrolling() { var x = 0; var y = 0;if (self.pageXOffset || self.pageYOffset) { x = self.pageXOffset; y = self.pageYOffset; } else if ((document.documentElement && document.documentElement.scrollLeft)||(document.documentElement && document.documentElement.scrollTop)) { x = document.documentElement.scrollLeft; y = document.documentElement.scrollTop; } else if (document.body) { x = document.body.scrollLeft; y = document.body.scrollTop; } return x + "," + y; } ////]]> </script></body></html> error[13:31:08,982]: Error parsing XML error[13:31:08,982]: Parse Error: Document is empty