Norton preventing web browsers from working

I have had Norton Internet Security running on my Windows 8 PC for over a year with no apparent issues. About a month ago I started experiencing problems with my web browsers - both IE11 and Chrome.  I had just had some big Windows 8.1 updates and at first attributed it to a glitch with these.  However, having looked into this and tried various fixes, nothing worked.  Then I saw a 'fix' that attributed similar problems to an antivirus software/firewall (not Norton) so I tried turning off the 'smart firewall' and 'browser protection' settings, and what do you know - everything works again!  However, I'm not particularly keen on leaving these turned off and my PC potentially at risk - after all what am I paying Norton for?

I couldn't find anything obvious on Norton's support website - so I'm trying in the Community.  Has anyone else had the same problems?

Thank you