In fact org.jboss.seam.jsf.ListDataModel delegates most of its functionality to javax.faces.model.ListDataModel (link broken when I write this; see also the API). The Seam code includes: private void readObject(ObjectInputStream ois) throws IOException, | ClassNotFoundException | { | this.setWrappedData( ois.readObject() ); | this.setRowIndex( ois.readInt() ); | } I assume readObject() throws an exception when the ObjectInputStream is not null but somehow emtpy, so I assume the readInt() could not yield -1 above, as writeObject sets it using getRowIndex(). Still: could using the wrong scope somehow mess this up...? Note that Order does implement serializable: @Entity | @Table(name="ORDERS") | public class Order implements Serializable Any thoughts welcome! Arjan. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4029243#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...