Exchange 2007 updates week of 10/7/2012 - Exchange down on reboot.
Small Business Server 2008 (Exchange 2007) updates from this past week's patch Tuesday are causing an interaction that is causing Microsoft Exchange System Attendant and Microsoft Exchange Information Store to not fire up. Hearing that two reboots may get you there. You can also fire them up manually in the Services MMC.
If you see the Microsoft Exchange System Attendant "starting," then you'll need to kill the mad.exe process from the Task Manager in order to get the services to start.