.
Thread 1 (process 6940):
#0  0x00007fedbb0c621f in gdk_window_set_opacity ()
   from /usr/lib/libgdk-x11-2.0.so.0
#1  0x00007fedbc5b5852 in ?? () from /usr/lib/libgksu2.so.0
#2  0x00007fedb9a283b4 in g_main_context_dispatch ()
   from /usr/lib/libglib-2.0.so.0
#3  0x00007fedb9a2b6c5 in ?? () from /usr/lib/libglib-2.0.so.0
#4  0x00007fedb9a2b9e5 in g_main_loop_run () from /usr/lib/libglib-2.0.so.0
#5  0x00007fedbb3d5f93 in gtk_dialog_run () from /usr/lib/libgtk-x11-2.0.so.0
#6  0x00007fedbc5b5c71 in report_failed_grab () from /usr/lib/libgksu2.so.0
#7  0x00007fedbc5b5f0d in grab_keyboard_and_mouse ()
   from /usr/lib/libgksu2.so.0
#8  0x00007fedbc5b636d in ?? () from /usr/lib/libgksu2.so.0
#9  0x00007fedbc5b357c in gksu_sudo_full () from /usr/lib/libgksu2.so.0
#10 0x0000000000404394 in ?? ()
#11 0x00007fedb928e1c4 in __libc_start_main () from /lib/libc.so.6
#12 0x0000000000402fb9 in ?? ()
#13 0x00007fffc49d9b98 in ?? ()
#14 0x0000000000000000 in ?? ()