Hi Harald,
This is related to a dbus bug, however dbus is quite a critical
component so updates to F12/13 haven't been provided so far.
There is an experimental repo, mentioned in the Email titled "Re: Dbus
upgrade? =>
http://repos.fedorapeople.org/repos/rdieter/dbus-backport/"
which at least worked really well on my machine :)
lg Clemens