****Update: December, 2010**** The October update issues have been addressed. See http://imperfectit.blogspot.com/2010/12/sharepoint-2010-october-cumulative.html
Just when we were thinking how it had been ages since a Microsoft update had broken our servers there are widespread reports of the October cumulative update wreaking havoc (User Profile Application in particular). Read the following from the SharePoint Team Blog to learn more:
We recommend installing http://support.microsoft.com/kb/2266423 followed by http://support.microsoft.com/kb/2352342 for now. As always, be sure to apply regular server OS security updates through Windows Update.