NuGet Package Manager errors when trying to update

Opening VS2010 today, the extension manager notified me of an update for NuGet Package Manager.

During the install, I get an 'Installation Failed' with an option to view the log.

The key error message I see in that log file is:

The signature on the update version of 'NuGet Package Manager' does not match 
the signature on the installed version. Therefore, Extension Manager cannot 
install the update.

The version numbers I am upgrading from/to are as follows.

Current Version: 1.5.20902.9026  
New Version: 1.6.21205.9031

I have also tried to install it while VS2010 is closed via this page: here

Update: The recently released NuGet 2.0 also may require uninstalling an older version of NuGet first.

From the NuGet 2.0 Release Notes: (http://docs.nuget.org/docs/release-notes/nuget-2.0)

Known Installation Issue

If you are running VS 2010 SP1, you might run into an installation error when attempting to upgrade NuGet if you have an older version installed.

The workaround is to simply uninstall NuGet and then install it from the VS Extension Gallery. See http://support.microsoft.com/kb/2581019 for more information, or to go directly to the VS hotfix.

Note: If Visual Studio won't allow you to uninstall the extension (the Uninstall button is disabled), then you likely need to restart Visual Studio using "Run as Administrator."

Here is the VisualStudio/Express hotfix for this issue... http://connect.microsoft.com/VisualStudio/Downloads/DownloadDetails.aspx?DownloadID=38654

There's not much on the page describing what it's for, but it's linked to from here that does provide some description... http://connect.microsoft.com/VisualStudio/Downloads

I have installed this hotfix on both the Professional (on Win 7 Pro 32 bit) and Express versions (on Windows 7 Ultimate 64 bit) and the NuGet update behaves as it should.

When i originally had the problem, Joe Doyle's answer solved it.

However, going to version 1.8, I cannot see a listing for nuget in Programs and Features.

So from within Visual Studio / Tools / Extension Manager.
Uninstalled NUGET.
Restarted VS Return to the Extension manager and install NUGET.

After uninstalling Nuget from Control panel, Go to C:\Program Files (x86)\Microsoft Visual Studio 10.0\Common7\IDE\Extensions\Microsoft Corporation\NuGet Package Manager\ or the location matching similar pattern based upon windows bit version, and delete the folder 1.0.11220.104. And, if you install it now, you wont' get the same problem.