It's probably Norton tripping over its own feet....as it is prone to do.
Try uninstalling Norton completely.
See if you can now access your emails/web correctly.
If so either reinstall Norton and run all the updates again.....or, as I have done myself and many other forum members too try the many freeware alternatives available.
I'm currently running Avasr av and Sunbelt/Kerio firewall with no problems to date.