Ich denke das hat was mit der Umstellung auf SSO zu tun.
Sametime benötigt diese, bzw stellt sie um.
Aus der Adminhilfe:
The SSO feature makes logging in and using multiple servers in a mixed environment easier for users. Use the following list to configure your Domino environment to ensure that your SSO configuration is successful.
General issues
URLs issued to servers configured for single sign-on must specify the full DNS server name, not the host name or IP address. For browsers to be able to send cookies to a group of servers, the DNS domain must be included in the cookie, and the DNS domain in the cookie must match the server URL. This is why cookies cannot be used across TCP/IP domains.
Clustered servers must have the full DNS server name in the host name field of the Web Site or Server document. This enables the Internet Cluster Manager (ICM) to redirect to cluster members using SSO. If the DNS server host name is not there, ICM will redirect URLs to clustered Web servers with only the TCP/IP host name, by default, and will not be able to send the cookie because the DNS domain is not included in the URL.
Bitte prüfe das ab.