Scan regularly stops running w/o warning

I have my system (Win 7) set up to run a full scan every night.  I have to check every morning that it actually ran.  Occasionally the light on the icon would turn red and then I would find that the scan hadn't run for a week!!!!  Why didn't it tell me as soon as there was a problem?  I have to reboot my computer and then the scan runs, for a few more days.  There is no problem with my Win XP system which has Norton configured the same way.  This is the latest version. 

 

In addition, and probably because of, I regularly receive viruses that delete my entire Thunderbird inbox.  When I delete the message with the virus it then deletes the trash as well. 

 

I am so frustated by these problems which never get fixed.  I think Norton is just coasting on its reputation at this point.  My subscription expires in 70 days and unless the situation gets better by then I will be switching to a different anti-virus.