Well, that's strange... Check the file ~/.config/xfce4/xfconf/xfce-perchannel-xml/xfce4-session.xml
, it should have a section that loads xfdesktop:
<property name="Client3_Command" type="array">
<value type="string" value="xfdesktop"/>
Alternatively, you can copy the file /etc/xfce/xdg/xfce4/xfconf/xfce-perchannel-xml/xfce4-session.xml
to your local directory (mentioned above). Make a backup of the file if you need to.
Hope that helps.