This sounds very much like https://bugzilla.xfce.org/show_bug.cgi?id=9193 which has a proposed workaround.
The crux of the problem is that thunar-volman tries to access information about the volume before the information is available. Adding a delay solves the problem, but not in a pleasant way. ** Bug watch added: Xfce Bugzilla #9193 https://bugzilla.xfce.org/show_bug.cgi?id=9193 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1210898 Title: Thunar does not automatically mount removable drives and media To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/thunar/+bug/1210898/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs