I am running a forum on phpBB which is updated to the latest version (3.0.11) and in the past I had used reCAPTCHA as a spambot countermeasure. Unfortunately even with that on, I am getting tons of spam fake accounts, a problem which has caused some problems sometimes.
Through googleing I found out that a lot of people were suggesting I used the "Custom Registration Question" as more reliable solution. Although I can create and edit those questions, whenever I change the settings to any other form of countermeasure than reCAPTCHA, I am getting this error:

So for the time being I keep using the reCAPTCHA to keep my forum functional.
Anyone has any idea or any suggestion of what might be the issue or how can I fix it? I tried so far reuploading the ucp_register.php and .html from a clean install but still, I had the same issue. So I don't know what else to do...
Any help would be very much appreciated!