ClassCastException raised when change portlet location on the fly

After I login as administrator, I change portlet's location(like move a portlet from right to left). But after I restart the web server, there is nothing change.

So I debug the JetSpeed 2, I found the problem happens in the class org.apache.jetspeed.page.impl.CastorXmlPageManager's registerPage() method. There is a java.lang.ClassCastException raised when registerPage() call setProfiledNodePathAndUrl() with cast the org.apache.jetspeed.om.page.Page to org.apache.jetspeed.page.document.AbstractNode.

It that some kind of configuration problem, but I did not change any default configuration.