<A href="http://ibmconnectionsblog.com/blog/connblog.nsf/dx/introducing-the-single-sign-on-diagnostic-tool-for-ibm-lotus-connections" target="_blank">SSO (single sign-on) can be difficult to set up properly.</A> IBM now provides a utility to help you check if things are set up correctly. This page includes a link to the wiki explaining how to set up and use the utility but it looks like you'll have to ask Support for it.