When i launch gnome-screensaver in gnome-terminal it doesn't work, and this is the output:

   1.
      process 5555: arguments to dbus_connection_send_with_reply_and_block() were incorrect, assertion "connection != NULL" failed in file dbus-connection.c line 3168.
   2.
      This is normally a bug in some application using the D-Bus library.
   3.
        /usr/lib/libdbus-1.so.3 [0xb7a61cde]
   4.
        /usr/lib/libdbus-1.so.3 [0xb7a610c7]
   5.
        /usr/lib/libdbus-1.so.3 [0xb7a555d6]
   6.
        /usr/lib/libdbus-1.so.3(dbus_connection_send_with_reply_and_block+0x1eb) [0xb7a33d4b]
   7.
        gnome-screensaver [0x8055629]
   8.
        /usr/lib/libgobject-2.0.so.0(g_type_create_instance+0x4b9) [0xb7982e29]
   9.
        /usr/lib/libgobject-2.0.so.0 [0xb7969fd2]
  10.
        /usr/lib/libgobject-2.0.so.0(g_object_newv+0x2db) [0xb796828b]
  11.
        /usr/lib/libgobject-2.0.so.0(g_object_new_valist+0x21f) [0xb7968def]
  12.
        /usr/lib/libgobject-2.0.so.0(g_object_new+0x40) [0xb7968fa0]
  13.
        gnome-screensaver(gs_listener_new+0x1c) [0x805344c]
  14.
        gnome-screensaver [0x8050743]
  15.
        /usr/lib/libgobject-2.0.so.0(g_type_create_instance+0x4b9) [0xb7982e29]
  16.
        /usr/lib/libgobject-2.0.so.0 [0xb7969fd2]
  17.
        /usr/lib/libgobject-2.0.so.0(g_object_newv+0x2db) [0xb796828b]
  18.
        /usr/lib/libgobject-2.0.so.0(g_object_new_valist+0x21f) [0xb7968def]
  19.
        /usr/lib/libgobject-2.0.so.0(g_object_new+0x40) [0xb7968fa0]
  20.
        gnome-screensaver(gs_monitor_new+0x1c) [0x804fafc]
  21.
        gnome-screensaver(main+0xe2) [0x804f862]
  22.
        /lib/libc.so.6(__libc_start_main+0xe0) [0xb7669970]
  23.
        gnome-screensaver [0x804f6f1]
  24.
      Aborted