Retrieving online highscores (following a guide)

I'm following this guide: http://wiki.unity3d.com/index.php/Server_Side_Highscores

I can post to my server just fine and see the scores in there, but retrieving them isn't working.

I have adapted the GetScores code as follows:

     private bool scoresDisplayed = false;
     private string highscoreURL = -omitted-;
     private string scores;

     void OnGUI()
     {
         if(GUI.Button(new Rect(500,500,150,50), "Leaderboard")) {
             scoresDisplayed = true;
         }
         if (scoresDisplayed) {
             GUI.Box(new Rect(800,500,150,50), scores);
             StartCoroutine(GetScores());
         }
     }
 
     IEnumerator GetScores()
     {
         scores = "Loading Scores";
         WWW hs_get = new WWW(highscoreURL);
         yield return hs_get;
         
         if (hs_get.error != null)
         {
             scores = "There was an error getting the high score: " + hs_get.error;
         }
         else
         {
             scores = hs_get.text; 
         }
     }

The box is displayed when I click on the Leaderboard button and says "Loading Scores", but nothing then happens.

I have tried both versions of the php code provided in the guide for display.php but that doesn't make a difference, and I know my database details are okay because it works for posting scores.

I did have an error in the console on an attempt as follows, and it came up 52 times, but don't know what it means:

 null != m_thread
 unityengine.www:.ctor(string)

Any pointers as to what I might be doing wrong will be appreciated. If you need to see more code, just ask, although I think this is all that's necessary along with the linked guide.