MSN is the leader in "relevant" content generation. If you have made sure to add content and make sure your site is relevant to the search key than dont worry. At times MSN might drop your site for a day or two while indexing other pages it seems, you will most likely see it back up within a few days. Also at times SE's may have other sites indexed but not published at the time of search, it is possible to get beat out by the competition. I suggest adding a little bit of new page content to secure your spot.