Microsoft screw third-party IM clients.

Microsoft intend to prevent anything except their own software communicating across the MSN Messenger network. This constitutes fair warning to anyone I know who uses only MSN Messenger - get a real IM client and network, now. For Windows, I understand Trillian is very nice. On Linux, I use gAIM which seems to work fine. As far as networks are concerned, I've found ICQ the most reliable, then Yahoo.