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 in Vista and they don’t always appear
immediately.
Download and run the Norton Removal Tool.
http://service1.symantec.com/SUPPORT/tsgeninfo.nsf/docid/2005033108162039
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Catherine said: