According to the KMess webpage, this problem should be fixed in version 2.0.6.1, which was released today (February 17th).
From the changelog: "Fixed login issues due to changes in the MSN protocol." -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
