Restlet 2.0 for GAE error: Couldn't write the XML representation

I spent a good day of troubleshooting app.nimbits.com trying to figure out why my web services on GAE were returning this error when i try to serialize an object into xml using   org.restlet.representation.Representation;

org.restlet.engine.http.adapter.ServerAdapter "Couldn't write the XML representation"

I first made sure i read the manual:

wiki.restlet.org/docs_2.0/13-restlet/275-restlet/252-restlet.html

but the manual here only give a GAE sample for returning a string, not a Representation.

The solution for me was to download

http://mirror.atlanticmetro.net/apache/xml/xalan-j/binaries/xalan-j_2_7_1-bin.zip

and add xalan.jar to my lib and classpath..

cheers!