I get the following error after an update from 6.x-2.3 to 6.x-2.5:

warning: call_user_func_array() [function.call-user-func-array]: First argument is expected to be a valid callback, 'page_title_admin_settings' was given in /homepages/35/d121417861/htdocs/flashgamesneu/includes/form.inc on line 377.

I looked it up, but the inc file seems to exist and is correct referenced in the module file.

I flushed all caches, but the error doesn't go away.
I could hotfix it ( for me ) but i'd like to now the reason for this problem, maybe i'm not the only one having it.