Ubuntu :: SUID And 'permission Denied'?

I have just installed 9.10 netbook remix onto my Eeepc 901. I was previously using 9.4 Rather than clicking on shutdown icons, or going through shutdown menus, I added a keyboard shortcut to run a shell script containing the following code:

Code:
#!/bin/bash
init 0
because init needs to be run as root to have the correct permissions, I set the owner and group to be root , ran chmod 711, then chmod u+s to prevent anyone altering the script, and to allow anyone to execute it with root privelidges Since updateing to 9.10 netbook remix, I have been unable to get this to work. have applied the above changes but get a "/bin/bash: /usr/bin/shutdownscript: permission denied" error when I try to run my shutdown script from the terminal (nothing happens when I press the key combination asigned to the keyboard shortcut). If I run the shutdown script with sudo then it neatly shuts down. ls reveals the following permissions:-rws--s--x 1 root root

So it appears as if SUID and SGID are both set, and the owner/group are correct, and the script works, and yet it doesn't have the permissions to work. I installed 9.4 long ago enough that I can't remember if I had to do anything else to get it working, or has something changed between 9.4 and 9.10?