Norton Security upgrade causing shutdown delay?

My Norton 360 expired last week and I installed Norton Security to replace it on 3 computers.  All installations appear to be successful but my HP laptop is having a shutdown problem.  When I shutdown Win7, it takes 30 - 40 minutes of hard drive activity before it powers down.  I have 2 Dell laptops that do not seem to be affected.  Has anyone else had this issue?

Thanks - Bill