|According to the MS website:|
When you try to install this security update (which was re-released August 9, 2011) by using Microsoft Update, you may receive an error code "66a." This error occurs when the following conditions are true:
o You have Microsoft Visual Studio 2005 Service Pack 1 (SP1) and Microsoft Visual Studio 2005 Premier Partner Edition SP1 installed on the computer.
o You have the original security update 2251481 offered by MS11-049 (released in June 2011) successfully installed on the computer.
To resolve this problem, uninstall the original security update 2251481 that was released in June 2011 and then install this security update that was re-released in August 2011. (Updates can be uninstalled by reviewing Installed Updates within Windows Update).
It worked for me!