Error When Running .NET 3.5 Web App: "The entry 'ScriptModule' has already been added."

Question

Title pretty much says it all. The web.config, unchanged from how VS2008SP1 generated it, has the following lines.

    <httpModules>
        <add name="ScriptModule" type="System.Web.Handlers.ScriptModule, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
    </httpModules>
<system.webServer>
    <validation validateIntegratedModeConfiguration="false"/>
    <modules>
        <remove name="ScriptModule"/>
        <add name="ScriptModule" preCondition="managedHandler" type="System.Web.Handlers.ScriptModule, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
    </modules>

The server is running .NET 2.0, 3.0, and 3.5 concurrently

Answer 1

Alter your <httpModules> section to first remove the key:

<httpModules>
    <remove name="ScriptModule"/>
    <add name="ScriptModule" type="System.Web.Handlers.ScriptModule, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
</httpModules>

That should ensure the error will go away.