my shutdown won't work

Recently I discovered a problem. Whenever I click on the
start button and click shutdown, it won't shutdown. The
box comes up asking if I want to restart, shutdown or
change users. I keep clicking on shutdown, and the box
disappears and nothing happens. When I hit the power
button on the computer, it hibernates. When I disable
hibernate, the computer does nothing. The only thing that
has worked is hitting the restart button, and the hitting
the power button while the computer reboots. Of course, I
know this is unsafe and can damage files. Is there a
simple solution, or any solution, to my problem? Thank
you.