Files required by the installer are not available in the Windows Installer cache.
Whenever a product is installed, a stripped down version of the original .msi file is saved in the Windows Installer cache (%windir%\installer). This .msi file is required, for updating, upgrading, or uninstalling the product. Error 1612 is generated when this .msi file is not available in the Windows Installer cache.
Run the Fixit utility, which can be downloaded from the Microsoft support website (http://support.microsoft.com/mats/Program_Install_and_Uninstall).