I have 12.04 freshly installed in my laptop. Recently I lost my rights as administrator. Hereare the problems: 1. unable to do updates from Update Manager (though no problem if I do it from terminal). 2. unable to shutdown/restart. When I press those buttons, I will only make the system logout. (no problem reboot/shutdown from terminal, though). 3. unable to store data into my FAT32 partitions. It says "Permission denied".
It seems I lost my administrator privileges from GUI menu.
Please help me. Thanks.