yep, temporary service down time is common..
however, I just did some tests, and it looks like MSNP18<->MSNP18 still works because it's using a 'tunneled sip' which means it doesn't dpeend anymore on that external vp.sip.messenger.msn.com server...
If I try from WLM to aMSN, it says "service is unavailable right now, please retry later"...
I might have been wrong, maybe you're right, they could drop the support, just like they seem to have stopped using that third party server for webcam when behind a NAT/firewall... They keep the support in the client, but they just bring down some servers that aren't needed anymore, which ends up breaking the support itself...
We'll have to wait a little to see if the server comes back online or not.. if it doesn't, then we're screwed

We'll have to either remove the feature or force the move to MSNP18... sucks!