|Something might have been put in your host file.|
Follow this path in your file system C > Windows > System32 > drivers >etc
Look for a file there called Hosts (just that, no file extension). Rename it to HostsX (which disables it) then restart your computer and see if you can then get to Norton.
If it doesn't help then rename it back. If it does help we can look further into the Hosts file entries.
Another place to look is IE Restricted Sites:
Tools > Internet Options > Security tab > Restricted sites icon, Sites button.
Always pop back and let us know the outcome - thanks