"Invalid Unicode value in one or more parameters" when using Social Bookmarking

I have a german Website. When the topic contains an "umlaut" (like ä, ö and ü) and i want to share it (twitter), i get the error: "Invalid Unicode value in one or more parameters"

What can i do?

Twitter simply doesn't support these characters. It is a limitation of twitter.

You can set up your board to replace all of them with regular characters, but that is probably not desirable.