NIS performance display will not come out of idle

At about 9:30 AM I started using my computer and after checking my e-mail I checked the performance display and found that it will not come out of idle, where the CPU screen is grayed out. Everything else seems to be working alright. This happened to me once before but it corrected after I did a live update and it said that there was one update waiting to be installed and needed to restart. This time I have run several live updates and it says that everything is up to date. I do not know how to re-start norton and I

have not tried to re-start my computer until I hear from one of you experts. By the way I always keep my machine on except for bad weather or taking it in for service.