Comment # 2 on bug 1210031 from Maurizio Galli

To me this sounds like a configuration conflict introduced by your backup copy. 


Logout of Xfce and log into a tty console and move the following file in your
home dir to backup location or delete it: 


~/.config/xfce4/xfconf/xfce-perchannel-xml/xfce4-session.xml

Log into Xfce again and see if everything works.