I know this has been covered, but none of the solutions appear to work for me.
I have ZCS version 5.0.13_GA_2791.Ubuntu8 network edition running on Ubuntu 8.04LTS.
The web interface works fine. Thunderbird email works fine. I cannot connect to any calendars using Windows XP (all updates) using thunderbird lightning (versions 126.96.36.199 and 0.9 respectively) nor Sunbird v0.9. I also tried a mac os 10.5.6 ical version 3.06.
Addresses I have tried are https://myserver/dav/username/Calendar
also https://ipaddress of server/dav/username/Calendar
also http://ipaddress of server/dave/username/Calendar
Iterations of the above included :443 after the servername and using the username@mydomain instead of just username.
So I'm guessing there is a setting on the server that I am missing.
All the server and workstations are behind a firewall so there are no firewall issues. All the server and workstations are on public ip space.
Web interface works fine.