System restart and shutdown wouldn't work

I entered restart on my system and then computer screen displayed 'Shutting Down'. It just sat there and would not finish shutting down and restarting like I requested. Does anyone know what causes this? I had to pull the wall plug to shut the pc see off. There wasn't any access to the keys and the power off buttton would not work when the screen was displaying 'Shutting Down'. I waited 40 minutes before pulling the plug just in case the system was going to eventually restart.

I am adding a little more information that may help in providing a solution to my problem.
On 11/18/12 after I discovered the restart hanging problem, I tried another restart after I pulled the plug and powered up again. The second restart worked normally (the system did not hang in the 'Sutting Down' screen). After a couple of hours of PC use, I tried a third restart and it worked normal. I did not shut the PC down when I finished using it on 11/18/12. On 11/19/12 after I clicked the mouse to wakeup the system from it's sleep mode, I proceeded to read e-mails, then I read a few news articles on the Google news site. I attempted a restart just to see what would happen. The system hung again just like it did on 11/18/12. The system just sat there displaying the 'Shutting Down' screen. After I pulled the wall plug to 'kill' the system, I plugged it back in, powered up and used it for about 10 minutes. I tried a restart to see what would happen and the restart worked normally with no problems. I also ran security scans that all came back normal. So sometimes the restart works and sometimes it doesn't work. What would cause this? What will fix this?

not sure if it helps or even if its related but i just had a similar issure when installing windows updates (.NET framework 4) im not a 100% if what was done has fixed mine yet so i have left the thread as unsolved (wont know until a windows update that needs system restarting comes in)

i will put a link to my post below. check it out see if it relates to your problem?

http://www.vistax64.com/general-discussion/298788-updated-laptop-hdd-problems.html

hope it helps you with yours

Hi Gene315,

Let’s try few troubleshooting steps to check if issue gets resolved:

1. Go to safe mode and check if it is working fine. Please use the following link for detailed instructions to go safe mode: http://www.vistax64.com/tutorials/123496-safe-mode.html
2. Perform clean boot to check if it would work, providing the link to do a clean boot for reference: How to perform a clean boot to troubleshoot a problem in Windows Vista or Windows 7

If issue persists, perform System Restore (only if Software Configuration Changes were made) providing the link for your reference: System Restore - Microsoft Windows

NOTE: With system restore you will not lose any data from the computer, any new programs installed in the computer has to be reinstalled on the computer.

Please post back the results.