www.domain.com was replaced by domain.com over a month ago in MSN. I also lost my #1 keyword ranking at the same time. I then implemented a non-www to www 301 redirect, but the change still hasn't come into play.
I also have a www / non-www dupe in their - even with the 301. The 301 was only put in right a week or two back (well... maybe a month) so I am not pannicking yet.
Actually - panicking won't help anyway. 301 is the RIGHT thingh to do to minimise links to the wrong URL regardless of what they do with the index. It seems that dealing with redirects is going to have to move up the agenda soon.