If you do enough installs or are just lucky - you are going to into the DSX exception. The symptom of this is that you can usually log into Profiles but you can't log into any of the other Connections applications.
Caused by: com.ibm.connections.directory.services.exception.DSException: com.ibm.connections.directory.services.exception.DSOutOfServiceException: com.ibm.connections.directory.services.exception.DSOutOfServiceException: CLFRK0004E: Directory Service Extension(DSX) received a HTTP response from URL 'https://something.com/profiles/dsx/instance.do?login=UID' expected XML, received unexpected content-type 'text/html;charset=UTF-8'!
The problem, for me at least, is that it is not clear at all what the exception means, much less what could be causing it. The worst part is that there are a lot of examples of people having this error but very few examples of them resolving it. This can lead to days of downtime trying to get things working
So here are some possible reasons for this
1) SSL key/certificate issues between the IHS plugin and the Websphere cell.
2) The connectionsAdmin account can't authenticate correctly. It may be necessary to remap some of the application admin roles. This didn't affect me but apparently it's possible.
3) The LotusConnections-config.xml interservice URL references are misconfigured. You can try setting them directly to the WAS server and port to avoid whole host of possible communication issues that could come into play
4) The SSO configuration is not properly setup. Make sure the domain is correctly identified and the SSO is enabled.
edit 4-23-14 -> 5) Almost forgot to add performance issues. The above issues deal with possible configuration. But if profiles (or communities) isn't available for performance reasons, you can expect to see the issue occur.
The core of the issue is that secure communication isn't being negotiated correctly for Profiles (or Communities) to validate the user account. If the above steps don't help, you can put the trace below on the application that's having the problem.