I am also having this problem (using Firefox 4.0beta 12):
Firefox has detected that the server is redirecting the request for this address in a way that will never complete.
This problem can sometimes be caused by disabling or refusing to accept
cookies.
Using FB in secure connection mode (i.e. https://www.facebook.com), it does not appear to be possible to use the Chess.com app. Attempts to access a game connection to https://secure.chess.com result in an infinite redirection of the URL. (Observed using Firefox 3.6.13 and Safari 5.0.3, under Mac OS 10.5.8.)