The problem must be in the /src/java/org/jivesoftware/spark/ui/status/StatusBar.java (298 line) - add custom message. It somehow ties in to the English names of the statuses, so when a user uses some other GUI language, it can't create a child menu with the saved status, as it can't find "Online", "Away" in the list of statuses, because they are translated.
That's a part of a wide problem with translated statuses. E.g. If you are using non-English GUI language, when it will append "Online" to every online contact in the list, though it normally doesn't append default statuses. But in this case for this user "Verfugbar" becomes his default for Online.