When i shutdown Xfce i get this errors:
** (xfdesktop:17728): CRITICAL **: settings_register_callback: assertion `cb && user_data && mcs_client' failed

** (xfdesktop:17728): CRITICAL **: settings_register_callback: assertion `cb && user_data && mcs_client' failed

someone know how to resolve this problem?
System: Slackware 12.1

i installed slackware without dbus & hal, i noticed it broke xfce & a few applications, it was not big deal to rebuild xfce & the qpplications without dbus & hal, but i dont see the error your getting since i rebuilt xfce, http://www.xfce.org/download/ get the graphical installer, it is basically all the source code packages bundled in to one large .run binary so it unpacks the source and loads a graphical tool to make it easier to build all packages in the correct order, dbus & hal are optional dependencies unless xfce was built with dbus & hal already installed then xfce wont run without dbus & hal...

the other applications i seen that needed to rebuild were CUPS and the Gimp & sane/xsane, there could be others i have not tried yet...

I get those same two messages after I logout of Xfce to console, along with xscreensaver complaining about something or other, and random other error messages. I got them with other distros as well. Someone told me it's just sloppy code in the WM. They don't actually cause me any problems that I'm aware of so I just ignore them.