I use a 3rd party MSN client. In the old days, I used Trillian, then MirandaIM and now Pidgin for the PC/Linux and Adium for the Mac. Both those clients give me the ability to use many different networks (ICQ, Facebook IM, Google Talk) at the same time using just one client. Plus I don’t have to tolerate the horrible adverts and pathetically large memory footprint of the official MSN client.
Today, presumably because they hate us, MS decided to change the protocol of their instant messaging network without telling anyone. This left many who use non-crappy clients without the ability to talk to their (usually less tech-savy) MSN friends. The reasons for MS doing this are unknown, but probably something to do with MS’s unwillingness to give any sort of control to OpenSource projects and those who believe that the MS products are inferior to the close-source alternatives.
Still, I have been given a fix for Pidgin at least (thanks Ed!). The plug-in based architecture of Pidgin allows a different MSN integration in the form of msn-pecan which, at the time of writing, allows previous service to be resumed. I think both Aidum and Pidgin teams are working on fixes for their clients. Now begins the work of getting my friends to use a rather more reliable IM network!
edit 12 Jan 9.10am: Due to the good people at Adium, it was a screw-up rather than an attempt to screw users. Everything is now back to usual it seems.