path /buddylist throws Access-Denied-Error on multilanguage drupal page

We tested the buddylist on our multilanguage-drupal-installation with the following (mysterious) result:

If a user (with preferred language-setting "en") visits the path "www.meineseite.net/en/buddylist/requests" or simply the path to "www.meineseite.net/en/buddylist" he is redirected to the Access Denied Page. If the user changes his language, he is able to see the page - so if he goes to the German version "www.meineseite.net/de/buddylist/requests" instead, he sees the wished Requestlist etc.

However, administrators always see every page and can always visit the path /buddylist.

We've checked all permission for the authorized users without any positive conclusion.

There must be some hidden clue to the path settings?!