Method 'get_EnableCdn' in type 'System.Web.UI.ScriptManager' from assembly 'System.Web.Extensions' does not have an implementation

I recently got an error when we upgraded a website from .Net 3.5 to 4.0. The site works perfectly fine on my dev environment which runs Windows 7, framework 4.0. But on the production server it doesn't. Ironically, the site on production server has been upgraded to framework 4.0 and works fine until I try to push updates by copying a published site. That's when I get this error. Error: "Method 'get_EnableCdn' in type 'System.Web.UI.ScriptManager' from assembly 'System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' does not have an implementation." Solution: The solution was to remove the following section from the web.config file:

<runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
        <dependentAssembly>
            <assemblyIdentity name="System.Web.Extensions" publicKeyToken="31bf3856ad364e35"/>
            <bindingRedirect oldVersion="1.0.0.0-1.1.0.0" newVersion="3.5.0.0"/>
        </dependentAssembly>
        <dependentAssembly>
            <assemblyIdentity name="System.Web.Extensions.Design" publicKeyToken="31bf3856ad364e35"/>
            <bindingRedirect oldVersion="1.0.0.0-1.1.0.0" newVersion="3.5.0.0"/>
        </dependentAssembly>
    </assemblyBinding>
</runtime>