i'm not sure if xfce is even to blame, but after recent updates my user lost permissions to mount external drives, control networking, restart and shutdown using panel buttons. is there a user group that has priviledges for all these things? i'm using the latest 4.10 from arch repos with archlinux and slim dm.
ok i got it.
not xfce as i partially suspected. this is my first machine using xfce full time and it is coming along nicely. keep up the good work!