Do you require application-intitiated update in the main window or the popup window? The complication that occurs here is that the asynchronous messages for both windows are shared by a single HTTP connection, and sometimes deadlock occurs (unless both windows are updated regularly). The ICEfaces asynchronous server will address this in an upcoming version.
If you don't require application-initiated updates, try enabling "synchronous mode" in your web.xml:
wel for example when I clik on an item in my tree view. I get the following error
SEVERE: Servlet.service() for servlet Blocking Servlet threw exception
at com.icesoft.faces.webapp.xmlhttp.BlockingServlet.service(Unknown Source)
I'm calling popup from another iface page indeed.