change wp-login-php back to wp-login.php ?

I cant change the link wp-login-php and i dont know where it came from, suddenly today, the link was change from wp-login.php into wp-login-php and now when i try to change the link it will not allow me to do so.

I have the latest buddypress and wordpress ... here is the link i cant change http://www.sorgogminde.dk/wp-login-php/ and that mean, users cant login.

How can a link change from .php to -php :disappointed: