Change to the /etc/opt/SUNWics5/cal/config directory.
In the ics.conf file, verify that the service.http.allowadminproxy parameter is set to "yes".
Check if the virtual domain is either set to "yes" or "no" in both the ics.conf and uwcauth.properties files. It cannot be "yes" in one file and "no" in the other file.
If you make edits to either the ics.conf or the uwcauth.properties files, restart Calendar Server.