I don't know much about dbus, and even less about qdbus, but might you need to specify :0 (or whatever screen you are using)?
on 11/06/2013 – Made popular on 11/06/2013
@cfr, you know you can simply use [[ -f /etc/profile ]] && . /etc/profile instead of the if/then statement. It will work either way, but I use the one liner because it makes my .xinitrc look a little cleaner.