Apparently, the latest set of Ubuntu updates may break it. That’s really not good. Microsoft would get flayed alive if a service pack broke Windows in this way. Dapper is a supported release; we need to do better than this. I’ve got no idea whether it’s a problem for everyone or just for a few people, and I don’t know how it’s being resolved, but I suspect some internal update-release procedures (as well as “how do we undo an update release” procedures) are being looked at. Meanwhile, don’t click the upgrade button just yet.