Have you hand-edited your /etc/gdm/gdm.conf-custom file?
I had and have left one section incomplete and had the exact same problem. When I deleted that file and did a "/etc/init.d/gdm restart" the shutdown and restart buttons reappeared.
You can also just reinstall the gdm package which will overwrite your gdm.conf-custom file with the default.
Have you hand-edited your /etc/gdm/ gdm.conf- custom file?
I had and have left one section incomplete and had the exact same problem. When I deleted that file and did a "/etc/init.d/gdm restart" the shutdown and restart buttons reappeared.
You can also just reinstall the gdm package which will overwrite your gdm.conf-custom file with the default.