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According to Microsoft KB2876415 is a rollup package for performance and reliability issues and correct other patches: http://support.microsoft.com/kb/2876415/en-us
In the past when having problems with dotnet updates I would install them in safe mode. Now Essexboy method is the best chance. Also there is a guy that deactivated avast! and WinPatrol ( no recomendable and I am not saying the issue is because avast! ) and was able to install it:
http://answers.microsoft.com/en-us/windows/forum/windows_8-windows_update/kb-2876415-will-not-install/c32d2773-b3ec-42c0-bf36-35f1f15e5946?auth=1