Hi!
I didn't get a response from the google server.
Replacing the following line in recaptchalib.php in function _submitHTTPGet
$response = file_get_contents($path . $req);
with
// create a new cURL resource
$ch = curl_init();
// set URL and other appropriate options
curl_setopt($ch, CURLOPT_URL, $path . $req);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
// grab URL and pass it to the browser
$response = curl_exec($ch);
// close cURL resource, and free up system resources
curl_close($ch);
fixed that problem.
Also replacing in Subs-Editor.php
fatal_lang_error('error_wrong_verification_code', false);
with
$verification_errors[] = 'wrong_verification_code';
led to a more convenient error handling.