I got this "500 Internal Server Error cloudflare-nginx" when attempting to send a score just now. I am using Firefox 7 and was playing Matlal's jewls. Interestingly my sp seem to have increased, so the score must have gone through despite the error notification.
It's just a little bug but it still saves your score and increases your sp. It happened to me in several games, not only at Matlal's jewl so don't worry for the next time you get the same error.
[font=cambria]