Dbus-monitor cannot detect reply message for system dbus

[007900800083 at citiz.net]

Hi:
         
          I use dbus-monitor to monitor method call and reply message on system dbus.
But I only get method call message, but can not any reply message. However i can get
both types of messages on session dbus with dbus-monitor.  I find someone has meet 
similiar issue in early version  http://lists.freedesktop.org/archives/dbus/2009-April/011146.html. 
Could someone kindly tell me how to fix it or it is a bug in system dbus.  Thanks a lot.

I am using dbus-1.5.8,  and system.conf is :

  <policy context="default">

    <!-- All users can connect to system bus -->
    <allow user="*"/>

    <!-- Holes must be punched in service configuration files for
         name ownership and sending method calls -->
    <deny own="*"/>
    <deny send_type="method_call"/>


    <!-- Signals and reply messages (method returns, errors) are allowed
         by default -->
    <allow send_type="signal"/>
    <allow send_requested_reply="true" send_type="method_return"/>
    <allow send_requested_reply="true" send_type="error"/>

    <!-- All messages may be received by default -->
    <allow receive_type="method_call"/>
    <allow receive_type="method_return"/>
    <allow receive_type="error"/>
    <allow receive_type="signal"/>

    <!-- Allow anyone to talk to the message bus -->
    <allow send_destination="org.freedesktop.DBus"/>
    <!-- But disallow some specific bus services -->
    <deny send_destination="org.freedesktop.DBus"
          send_interface="org.freedesktop.DBus"
          send_member="UpdateActivationEnvironment"/>


    <!-- Allow everything to be sent -->
    <allow send_destination="*" eavesdrop="true"/>
    <!-- Allow everything to be received -->
    <allow eavesdrop="true"/>
    <!-- Allow anyone to own anything -->
    <allow own="*"/>
</policy>


Cheers
Liang.