I suspect this is a bug in GTK+2, which is still not fixed upstream. They've fixed it in GTK+3 only, that's why in MATE GTK+3 mate-display-properties doesn't crash.
I've linked the upstream bug report here. ** Bug watch added: GNOME Bug Tracker #635380 https://bugzilla.gnome.org/show_bug.cgi?id=635380 ** Also affects: gtk via https://bugzilla.gnome.org/show_bug.cgi?id=635380 Importance: Unknown Status: Unknown ** Also affects: gtk+2.0 (Ubuntu) Importance: Undecided Status: New -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1351890 Title: Changing external screen resolution with dual monitors To manage notifications about this bug go to: https://bugs.launchpad.net/gtk/+bug/1351890/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs