At first I think, it doesn't work since May 30th. That's the date where the last score was submitted and it would surprise me if it haven't been used since on a daily base (at least some game).
Tested with Firefox (39.0), Chrome (43.0.2357.134 m), IE (11.0.9600.17914), all the same behavior.
Tested games: Tetris and "1 in 24 Speed v32"
After finishing the game a blank screen appears:
Now when trying to leave the site the warning message appears ("Do you want to really leave this site"... somewhat in that, I'm using a German browser^^).
When now trying to start another game the following message is displayed.
That said, I think, the second pic describes a problem that's following from the first one.