Server Based High Score - issues with adding new score

Hi,

I'm following this tutorial, having no prior experience with networking, databases etc.. http://gamedev.stackexchange.com/questions/53566/server-based-high-scores

I almost got it working, except for the running the addscore.php script. Here's my slightly modified PostScores() coroutine:

 public static IEnumerator PostScores(string name, int score, int rank)
 {
     //This connects to a server side php script that will add the name and score to a MySQL DB.
     // Supply it with a string representing the players name and the players score.
     string hash = Utility.Md5Sum(name + score + secretKey);

     string post_url = addScoreURL + "name=" + WWW.EscapeURL(name) + "&score=" + score + "&rank=" + rank + "&hash=" + hash;

     print (post_url);
     // Post the URL to the site and create a download object to get the result.
     WWW hs_post = new WWW(post_url);
     yield return hs_post; // Wait until the download is done

     if (hs_post.error != null)
     {
         print("There was an error posting the high score: " + hs_post.error);
     }
 }

So, the interesting part is that when I print the url thing and copy-paste it in my browser it works fine. I can see new entries added in my database and then the other script reads them correctly in my game. So, I suspect it's these lines that seem to be rogue:

  WWW hs_post = new WWW(post_url);
  yield return hs_post; // Wait until the download is done

This is all new stuff for me - I don't even understand the coroutines fully. I also get no errors, so no clue what's wrong. I can't be asking my players to copy-paste the generated url in their browser every time, can I? ;) :D

Thanks in advance,