Okay, this is based on research (and I fear my answer will be rather technical), but your problem seems to be caused by
dbus, a way for applications to communicate with other applications (so-called inter-process communication, you can learn about it on Wikipedia). People had this problem in the past with Nautilus (the GNOME file manager) as well (there is a bug report on the GNOME bug tracker about that problem, unfortunately it does not hold any solution).
So, is there any solution / answer to this? Not really, as we cannot pin down the application that is not responding via
dbus (at least not without diving deep into the source code and start debugging). My assumption is it is related to
gvfs (a virtual filesystem, providing access to files from various sources, for example via
NFS or other protocols). If you have external file sources (for example any network location) in Files and the problem persists, you could try to remove these network locations.
Additionally, if the problem persists, you should open a bug report on Launchpad, so the developers can try to track it down. If the problem does not persist, something went wrong (this does happen sometimes, it's hard to track down those hiccups), but everything should be fine, at least after a reboot.