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I'm using KDM as a KDE user. today I have installed xfce and had this problem. Just checked if had gvfs and polkit-gnome installed. gvfs was already on my system but polkit-gnome didn't so I installed it and relogged in. Everything worked fine now with wonder's suggestions
1) fix your ~/.xinitrc. it should ONLY contain the line exec ck-launch-session startxfce4
2) install polkit-gnome and relogin
3) be sure that /usr/lib/polkit-gnome/polkit-gnome-authentication-agent-1 runs and if not, run it manually or from whatever xfce has to do it automatically at login,
4) thunar-volman is deprecated, install gvfs
PS.: we don't use initscripts anymore so I did omited step 1. Checked step 3 after installing polkit-gnome and relogin; it was running.
Hope this could be useful as an update.
Juan Antonio Cánovas
Spanish Arch Linux community team
www.archlinux-es.org || Comunidad Hispana de Arch Linux
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