The SharePoint Team blog posted a notice Friday (11/5), that there was an issue with the SPS2010 October CU, and to not install it. Cryptically, they said if you have installed it, to contact Microsoft Support.
Later in the day, they posted a follow-up, detailing which packages were affected (SharePoint Server Package 2394320 and Project Server Package 2394322), and steps for a workaround.
It appears that the main issue is that the User Profile Service Application loses the assigned permissions during the install of the CU. The post walks you through resetting the permissions.