There is a duplicate 'system.web.extensions/scripting/scriptResourceHandler' section defined

I am trying to create an MVC2 web application that will run both on my local development machine (on localhost), and on our central webserver.

Development machine:

• Windows 7 Professional, 64bit
• Visual Studio 2010 (beta)
• ASP.NET 4.0
• IIS 7.5
  

Webserver:

• Windows Server 2003 SP2
• ASP.NET 3.5 SP1 (determined by checking the folders under %SystemRoot%\Microsoft.NET\Framework)
• IIS 6.0
  

Everything works fine when debugging from VS, and I've finally gotten so far that it also works copied to the webserver. However, when I try to copy it to my own local webserver, I get the following error message:

13:  <sectionGroup name="scripting" type="System.Web.Configuration.ScriptingSectionGroup, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35">   14:  <section name="scriptResourceHandler" type="System.Web.Configuration.ScriptingScriptResourceHandlerSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="MachineToApplication"/>
   15:  <sectionGroup name="webServices" type="System.Web.Configuration.ScriptingWebServicesSectionGroup, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35">

It almost goes without saying, I can not see any duplicate scriptResourceHandler section at all!

The application I am testing on, is the default application that is created when you use the ASP.NET MVC2 Web Application template. The target framework for the application is .NET 3.5. (Because it has to run on our central .NET 3.5 webserver.)

Is see now that I a comparable error message when trying to configure the web application in IIS7:

There was an error while performing this operation.

Details:

Filename: \\?\C:\Temp\test2\web.config
Line number: 14
Error: There is a duplicate 'system.web.extensions/scripting/scriptResourceHandler' section defined