Forum Moderators: mack
A big drop at once could mean a change in algo or a large addition to their indexed pages at one time. Or, maybe, someone reported your site as spammy, MSN looked at it, then gave you a penalty. A gradual change would mean MSN is finding new pages and putting them ahead of yours.
I don't have any experience with my pages declining in SERPs at MSN, just an increase in traffic as more of my pages are indexed.