Computer wont shut down

I have a user that when he goes to Start > Shut Down and choose to shut down the computer just looks like its frozen and stays like that. So we told him to do the ctrl+alt+del and choose shut down from there. That was working for him fine up until I think last week.

He does the crtl+alt+del and then it looks like it freezes and when you hit the shut down button it looks like its about to shut down then about 5 minutes later the screen appears like youve just hit ctrl+alt+del. So it lets you hit the shut down button again but does the same thing and wont shut down.

So the way he is turning his computer off he is holding in the button. Thats the only way it will shut down.

Anyone know how we could fix this? suggestions?