I know probably everyone else in here knows this, but I figured I would let those of us who need to ride the short bus in on it too. If you have installed Plesk 7.5.5 recently, you know that you have SiteBuilder installed as well. Well, while cleaning up some things on the server, we saw that MSSql was on. In earlier versions, it was never used and we could turn it off and not cause any problems. Turns out you shouldn't do this if you have SiteBuilder installed. SiteBuilder uses MSSql. You won't be able to create any new domains (if the SiteBuilder box is checked) without it running. You'll get an error about how it cannot find the SQL database. Anyway, these are my experiences. Hope it helps somebody!