If you have special characters (e.g. German umlaut) as part of the Lotus Notes user name and are using Lotus Quickr (Domino Services) you might experience problems with the Quickr connectors.
As soon as you add a user who has a special character in his name as a Superuser of to place, all users who have access to this place will no longer see any places in their connector list.
The problem is already reported to developement.
The only currently available workaround is to give a maximum of Manager access to such users.
This again shows that it is a good recommendation not to use special characters for user names ....