That happens to me allot on multiple games. I found a way around it though. I will try to explain using examples. Okay, here it goes.
Let say , I am playing Snake , And I get 2nd place, the first time. And after that I play a second game, then get 1st place. The problem comes when I click the submit score button , in order to record my score into the Mili Forum Arcade.
The thing that works for me is to log off my browser, then log back in and come back to the miliforums and play it again, then, If I beat my 2nd place score, then I can now put in my 1st place score.
I do not know it this will help you, but it has worked for me. I know how it feels to get a good score on the first go around, but then get a better score on the second go around, but then having a message telling you that your score will not be saved.