Search for the qtranslate-core.php in the plugins folder, and delete from line 106 to line 110:
// Check for WP Secret Key Missmatch
if($wp_default_secret_key != AUTH_KEY) {
global $error;
$error = __(‘Your $wp_default_secret_key is mismatchting with your AUTH_KEY. This might cause you not to be able to login anymore.’,’qtranslate’);
}
That’s what’s causing the problem.