Some users have accounts with umlaut characters (ä, ö, ü etc.) in their login name. When clicking on the user in the user list of the admin dialog an error message is displayed "The user M ller does not exist". It is now impossible to modify their entries.

Although special characters are no longer allowed in JIRA 2.6.1, we have existing users which still have login names with umlauts, who created their accounts with earlier JIRA releases.