I think this is a network-manager bug after all. Dbus isn't crashing at all. I've submitted the bugreport:
https://launchpad.net/distros/ubuntu/+source/network-manager/+bug/57689 -- Sometimes DBus fails to reload after resuming from suspend-to-RAM https://launchpad.net/bugs/27638 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
