Error installing SharePoint 2010 RTM after uninstall of Beta

I decided to save myself some time by installing SharePoint 2010 RTM on a server that was previously running 2010 beta. Lets just say that it was not so short and simple…

License upgrade in Central Administration. LICENSE UPDATE FAILED

Install RTM over Beta. PSCONFIG FAILED

Uninstall beta and install RTM. PSCONFIG FAILED

Ok… Now what? Lets take a look at the event viewer…

Description:
Failed to create the configuration database.
An exception of type System.InvalidCastException was thrown.  Additional exception information: Unable to cast object of type 'Microsoft.IdentityModel.Configuration.MicrosoftIdentityModelSection' to type 'Microsoft.IdentityModel.Configuration.MicrosoftIdentityModelSection'.

Seriously?! A .NET error… Gimmie a break. After reregistering .NET I ran across another blog that addressed the issue.

http://www.sharepointassist.com/2010/07/14/geneva-error-exception-system-invalidcastexception-unable-to-cast-object-of-type-microsoft-identitymodel-configuration-microsoftidentitymodelsection-to-type-microsoft-identitymodel-configura/

SOLUTION:

Open the web.config file (C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\WebServices\Root) and manually update your .NET version from 1.0.0.0 to 3.5.0.0.

<section name="microsoft.identityModel" type="Microsoft.IdentityModel.Configuration.MicrosoftIdentityModelSection, Microsoft.IdentityModel, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>

Create a new ConfigDB next time you run PSCONFIG.