Norton Security Suite Disappears

I have NSS through Comcast running on a Windows 7-64 PC.  The SysTray icon suddenly disappears and the Norton software stops working (i.e. can't manually start the program).  I read about this problem on other forums, which recommend removing the software and reinstalling.  I have done this on several occasions and it works for ahile, but then the problem reoccurs.

 

What should I do?