If you were in chat and can't seem to get back in, first try logging off of SGS, clearing your browsers cache file and then logging back in.

If you did not log out of SGS on a previous session but closed your browser window instead and then came back later and logged in again you might have problems getting into chat. Always log out of SGS when leaving to avoid being logged in twice... you might notice sometimes people show up twice in the Who's online box.