I just tell about my problem now here and in the Google group. Perhaps someone in charge reads it.
I have the issue that my calls to the API get blacklisted. Please take a look: http://www.newgrounds.com/projects/games/1109814/preview - password is v3beta
If you play the game, you will see that it does not do many calls but already the second call (when a game is started) normally gets rejected. Users won't be enthusastic if their medals and scores were not submitted. :-(
Benjamin