As you will see from my signature at the foot of this post, I have XFCE installed on this laptop - along with three other versions of PCLinuxOS.
After I read your post, I rebooted into XFCE and then logged out. I have to report that the switch off went flawlessly. I do, however, find a similar problem with my installation of Open Box.
Sorry, I can't give you an answer on this problem.