Windows 7 logging off when "shut down" is pressed
I'm having a widespread issue on all of our student's Windows 7 x64 laptops where when "shut down" is pressed, the laptop will log off and return to the Ctrl-Alt-Del prompt.
This is happening on both partitions of the laptop; one connected to the domain for school use, and the other standalone for home use.
I can't find any issues with the Group Policy settings or anything in Control Panel.
The problem is temperamental - the same machines that are faulty one day are fine the next.
There are 3 administrator desktops with windows 7 that don't display the issue.
Is there something I might have overlooked? what is there that's different between our desktops and the student laptops that could cause the problem?
Thanks in advance