Same problem. Reading info file above was no help. The error log says:
[KB2686509.log]
4.907: ================================================================================
4.907: 2012/05/08 22:19:01.421 (local)
4.907: C:\WINDOWS\SoftwareDistribution\Download\3438087687b5dd8accc81e44f72f02e7\update\update.exe (version 6.3.13.0)
4.938: DoInstallation: GetProcAddress(InitializeCustomizationDLL) Returned: 0x7f
4.938: Failed To Enable SE_SHUTDOWN_PRIVILEGE
4.953: Hotfix started with following command line: -q -z -er /ParentInfo:b1124e1cfa703842a1c4559538c4644b
4.969: In Function GetReleaseSet, line 1211, RegOpenKeyEx failed with error 0x2
4.969: In Function GetReleaseSet, line 1240, RegOpenKeyEx failed with error 0x2
9.172: Return Value From IsMachineSafe = 0
9.172: IsMachineSafe returned 441092
9.172: Fist Condition in Prereq.IsMachineSafe.Section Failed
9.172: Condition Check for Line 1 of PreRequisite returned FALSE
9.188: ReadStringFromInf: UpdSpGetLineText failed: 0xe0000102
9.188: 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
9.203: ReadStringFromInf: UpdSpGetLineText failed: 0xe0000102
9.203: Setup cannot continue because one or more prerequisites required to install KB2686509 failed. For More details check the Log File c:\windows\KB2686509.log
9.203: Update.exe extended error code = 0xf0f4
16.516: ================================================================================
What next? Thanks...