I was recently having this trouble as well (Chat and friends offline, everything else good). While my network configuration is far beyond most basic users setups, it allowed me to do some deep digging into some detailed logs on my firewall. It turns out, in my case anyways, that my firewall was ignoring (not even blocking) connections on TCP 9000. This port is apparently used (and unpublished) for chat and friends. Fair warning though, this port is frequently used to propagate email worms and viruses as well as being used for a few remote access 'hacks'. ****Make sure your antivirus software and definitions are up to date!!****