Tried via the windows update bubble, running windows update and downloading from http://www.microsoft.com/en-us/download/confirmation.aspx?id=29804
All failed. Log extract is below - any help appreciated.
17.328: 2012/08/07 21:39:38.093 (local)
17.328: e:\f233283453ffec0db9fe5d\update\update.exe (version 6.3.13.0)
17.453: DoInstallation: GetProcAddress(InitializeCustomizationDLL) Returned: 0x7f
17.468: Hotfix started with following command line:
17.515: In Function GetReleaseSet, line 1211, RegOpenKeyEx failed with error 0x2
17.515: In Function GetReleaseSet, line 1240, RegOpenKeyEx failed with error 0x2
17.625: CreateUserInterface: GetProcAddress for DefineInstallCustomUI failed: 0x7f
19.343: Return Value From IsMachineSafe = 0
19.343: IsMachineSafe returned 506628
19.343: Fist Condition in Prereq.IsMachineSafe.Section Failed
19.343: Condition Check for Line 1 of PreRequisite returned FALSE
19.359: ReadStringFromInf: UpdSpGetLineText failed: 0xe0000102
19.359: KB2686509 Setup encountered an error: Setup cannot continue because one or more prerequisites required to install KB2686509 failed. For More details check the Log File c:\windows\KB2686509.log
19.531: ReadStringFromInf: UpdSpGetLineText failed: 0xe0000102
19.531: Setup cannot continue because one or more prerequisites required to install KB2686509 failed. For More details check the Log File c:\windows\KB2686509.log
... 
