Support for Windows Vista Service Pack 1 (SP1) ends on July 12, 2011. To continue receiving security updates for Windows, make sure you're running Windows Vista with Service Pack 2 (SP2). For more information, refer to this Microsoft web page: Support is ending for some versions of Windows.
An update for the Microsoft .NET Framework version 4 may not install if the following conditions are true:
You previously installed the Microsoft .NET Framework 4 or the Microsoft .NET Framework 4 Client Profile.
A system restart is pending but has not been completed before you install the new update.
Note If you install the update by using the Windows Update site, it may seem that the update was offered and installed. However, after you restart the computer, the same update is offered again.
This issue occurs because, when the Microsoft .NET Framework 4 is installed, certain components are locked or are being used until the system is restarted. These components cannot be updated until the system is restarted. Because of this, in the scenario described in the Symptoms section, the version of the shim (mscoree.dll) is the Microsoft .NET Framework version 3.5 SP1 or earlier. The installation of the Microsoft .NET Framework 4 deploys certain settings which prevent the older shim from working correctly until the shim is updated after the system is restarted. In this scenario, if you try to install another update for the Microsoft .NET Framework while the restart is pending, the update will try to use a Global Assembly Cache (GAC) deployment for the files in the update. This GAC operation requires the shim. However, because the shim is in an inconsistent state pending a restart, the GAC operation will fail. This causes the update to fail.
To avoid this issue, restart the system before you install the new Microsoft .NET Framework updates. If you have already experienced the condition, and an update did not install because of this issue, restart the computer and then reinstall the new updates.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.