Problem with Dell Inspiron 1520 - dual boot: Windows XP and Ubuntu. After updating Ubuntu 11.10 to Ubuntu 12.04 shutdown->restart function is not working. Another problem: starting Grub (version 0.97) menu screen shows old Ubuntu 11.10 entries. After selecting 11.10 entry, Logon screen shows Ubuntu 12.04 title. Restart function does not work before or after logon - in both Unity and Gnome Classic (no effects) desktops. Terminal command: "sudo reboot" works; "sudo shutdown -r now" does not work most of the time. Problems corrected in Ubuntu 12.10 !!!
Firstly; to update grub, run
sudo grub-install /dev/sda (assuming /dev/sda is your hdd)
as for the restart, if you click the "shut down" button, restart is an option on the dialog which pops up.