<A target="_blank" href="http://www.eknori.de/2010-08-09/upgrading-from-sametime-8-5-to-8-5-1-read-this/">Ulrich Krause ran into some problems upgrading from Sametime 8.5 to 8.5.1</A> that took him a couple of days to figure out. He's posted his findings to help you avoid the same issue.