If you login to a GNOME session, then logout, then immediately login again, during this second session many crucial environment variables, such as DBUS and GnomeKeyring socket paths, are stale: they still have the values corresponding to the old session.

This happens when bonobo-activation-server, for some reason (e.g. it still has a registered service), doesn't quit on logout, and so next time b-a-s launches deskbar, deskbar inherits the environment of b-a-s, which hasn't changed since the  last session.

The solution is to add the following attribute[1] to the applet factory in the .server file:

        <oaf_attribute name="bonobo:environment" type="stringv">
             <item value="DBUS_SESSION_BUS_ADDRESS"/>
             <item value="GNOME_KEYRING_SOCKET"/>
             <item value="GPG_AGENT_INFO"/>
             <item value="SESSION_MANAGER"/>
        </oaf_attribute>

[1] as documented in http://developer.gnome.org/doc/API/2.0/bonobo-activation/attribute-tag.html