But a number of other problems still exist when running Norton Internet Security. I am running NIS 2003 so I am not sure of the settings in other versions. I spent a while trying to isolate why I could not edit events on my home PC. It seems that in the NIS Options on the Firewall tab if you uncheck the “Stealth blocked ports” check box then you can edit events in Google Calendar.
Based on the help provided with NIS “Stealth blocked ports“:-
Blocked and inactive ports do not respond to connection attempts. Active ports do not respond to connection attempts with incorrect source or destination information.