The Connections Blog

Now this is a really tricky area, configuring SSO in Lotus Connections - in my experience, getting Connections and Quickr/Domino in SSO harmony is a particular area of pain.  Here's a cracking little developerWorks whitepaper detailing how it should be done in a standalone Connections environment:

This article explains how to configure single sign-on (SSO) with Lightweight Third-Party Authentication (LTPA) for IBM Lotus Connections 2.0. Learn the basics of SSO and LTPA and the detailed steps for configuring SSO in a stand-alone environment.

Single sign-on (SSO) can be complex to configure, but it is beneficial to users who otherwise become annoyed when repeatedly queried for login information. Using the new home page feature in Lotus Connections 2.0, you can easily switch between different features, but you must enable SSO to connect to them seamlessly.

Of particular importance is getting the domain name right - you must add the leading dot, else behaviour can be very variable, especially in Communities Forums:

Well recommended.