Memberlist doesn't work after update

After updateing phpbb version to 3.0.10 (1thank style) memberlist doesn't work right.
If i open memberlist and select as example letter "b" then it says
Not Found

The requested URL /forum/memberlist.php&first_char=f was not found on this server.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

Hope you guys know how to fix that. That is quite annoying