Windows Update - Out of Band Enhancements (11/25/09)
The ISC has a great summary related to important updates that should be applied to keep Windows updated. These are more functional than security related. This may be the reason they were published outside the Patch Tuesday process. I've experienced no issues after applying these changes (which required rebooting).
Microsoft Updates requiring reboot
QUOTE: We've been informed by several readers that they've received updates from Microsoft in the last 24 hours (via Automatic Update or similar) that required a reboot. Microsoft has apparently updated several of their bulletins. Two of them are related to previous updates MSXML (v3.0 or v6.0), one with MSXML Core Services 4.0 SP2, one is additional daylight saving time updates, and the 4th is also daylight saving time-related and has to do with an error in the Date and Time control panel on Vista and Windows Server 2008. While it isn't unusual for Microsoft to make some minor updates to bulletins and patches (especially detection fixes) at times other than "Patch Tuesday" some of our readers (and some of us, handlers) were surprised by updates that required reboot.
Microsoft KB 973685
Microsoft KB 973687
Microsoft KB 973688
Microsoft KB 976098
Microsoft KB 976470