There are some reasons your chat might not be working, one is that you are behind an internet proxy (usually at work) which prevents the type of communication we're using. In that case there isn't much you can do unless you know the administrator of your network.
Another reason might be that your firewall is preventing communication over port 843, a simple exception in your firewall settings for this port should solve the issue. Port 843 is supposed to be a standard port reserved for Adobe, it is required to open socket connections in Flash.
