Norton is likely causing your problem.
Replace Norton with the free AVG
http://free.grisoft.com/ or Avast
http://www.avast.com/eng/avast_4_home.html, and Windows Firewall and Windows
Defender. Disabling Norton is not enough. You need to completely uninstall
it. If it doesn't solve the problem, get rid of Norton anyway. Norton is
known to cause many problems which don’t always appear immediately.
Download and run the Norton Removal Tool.
http://service1.symantec.com/SUPPORT/tsgeninfo.nsf/docid/2005033108162039
It's called "360" because Symantec's goal is complete ownership of your
computer, and with even less communication about what it's trying to do or
ways to configure it than ever before (which would only interfere with its
goal.) That, along with Symantec's famous technical support, makes Norton
360 a disaster that I would only install on Granny's computer if she was
going to disinherit me.