For a wider readership:

> 
>     I recently had issues where Firefox and the SpaceFM file manager would
> hang when started. Apparently they were calling dbus-launch.
> 

If they were calling dbus-launch, that means that they were unable to contact a
Desktop Bus broker and tried to run their own broker in the same session as
themselves.  Run system-control status dbus and system-control --user status
dbus to check that the system-wide and your per-user Desktop Bus brokers are
running and to see their logs.  Also look at /run/dbus/ and whether you have a
DBUS_SYSTEM_BUS_ADDRESS variable pointing at a different place.

I cannot speak to Firefox but a quick check with SpaceFM reveals that, once it
can contact a Desktop Bus broker, it tries to contact and auto-start the
org.freedesktop.UDisks2 server over the system-wide Desktop Bus.  So you'll need
a system-wide org.freedesktop.UDisks2 service that runs that server.  I've added
such a service bundle for 1.36.