Heiko, yes it is a .Net problem. The XMLSerializer class in the .NET Framework 2.0 has a bug with optional elements. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4041748#4041748 Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&p=4041748