The aracde modification doesn't have anything to do with this hack. As far as the date thing goes, I don't know what the german language uses so I couldn't change that. Just use whatever you use elsewhere on your site for the date and time part of it.
As far as the other problems go, you are the first that has reported that so I'm not sure exactly what is going on. Have you updated your counters recently? You might want to try that and see if that fixes the problem, especially if you have deleted any users that were top posters in a forum at one time. Let me know.