I had the same problem and I couldn't figure out what the heck was going on, but now it all makes sense, the weird thing is though other games are working fine, I had this issue with just one game as far as I know.
I like the high-score function it's great, it's a fun community feature. Since there will always be people that will try to cheat, I support every kind of measures against it!
Is there a way to turn high-score of in BigBox? Because my kids also play these games and a lot of the times they want to continue where they left of, specially when playing with friends.
It would be cool if you could launch a game with or without high-score enabled or if one could enable/disable it with a hotkey.
Anyways, thanks for the clarifying things up! Finally know where this error is coming from!