show special characters from windows-clients

when nicknames from windows-clients contain special characters, the whole name is dropped. I think because of drupal_validate_utf8 ( http://api.drupal.org/api/function/drupal_validate_utf8/5 )

a client inserts the æ by switching the keyboard layout to danish and inserts this symbol with the ü-key (german keyboard). he does not do the "alt+number"-combo thing.

afterwards the teamspeak block only shows a green dot without name. if I do the same thing on my linux-box by "alt gr+ a", everything works fine.

maybe a conversion needs to be done, before passing it to the utf8 filter?