Hang while shutting down.

I've searched for an answer here and on other sites but came up empty. Here goes. My boss has a Dell laptop Insipron 6400 Windows XP. I can't get it to shut down unless I hard boot. It won't restart or shut down. What I think is different then most is that it starts to shut down( removes the icons) then just sits there with just the desktop staring at me.No error messages, no end now windows. I can move the mouse. I tried leaving Task Manager open but it closes right before it hangs.
I have done a memory test and all is good. I have used malewarebytes, spybot, adware, and CC Cleaner. I have AVG and Zone Alarm. Any thoughts?

 

Does it shutdown or reboot properly from Safe Mode?

 

Yes it does shut down in safe mode

 

Any ideas?

 

If your using norton antivirus 360 version 2 that might be cause the problem.