Fatal Error redeclare user_can_create_post

Hello!

this is the error that I get when I go to http://www.hibi.org.uk/home
I can not log in to my wp anymore. Does anyone know what to do?

This is the error:

Fatal error: Cannot redeclare user_can_create_post() (previously declared in /data/members/paid/h/i/hibi.org.uk/htdocs/www/home/wp-includes/functions-post.php:339) in /data/members/paid/h/i/hibi.org.uk/htdocs/www/home/wp-includes/capabilities.php on line 356

And this is a part of the wp-includes:

}

/* returns true if $user_id can edit $post_id */
function user_can_edit_post($user_id, $post_id, $blog_id = 1) {
$author_data = get_userdata($user_id);
$post = get_post($post_id);
$post_author_data = get_userdata($post->post_author);

if ( (($user_id == $post_author_data->ID) && !($post->post_status == ‘publish’ && $author_data->user_level < 2))
|| ($author_data->user_level > $post_author_data->user_level)
|| ($author_data->user_level >= 10) ) {
return true;
} else {
return false;
}
}

Thank you very much!