Mixing MVC3 application with Classic Form ASP .NET application on IIS 7.5

We are currently trying to configure IIS 7.5 to run 2 applications (one MVC 3 .NET 4 and one Asp .NET forms .NET 2) onto the same structure.

The config is as follow:

Physical Path:

Drive
+--- Root
     + Web.config
+--- Sub
     + Web.config

IIS Config:
Root App (MVC 3 based on .NET 4 AppPool)
  ¦
  +Sub App (Classic ASP .NET based on .NET 2 AppPool)

This was working perfectly fine on IIS 6. However, making the same config on IIS 7.5 fails.

The Root App is working fine but the Sub App is failing to start. The error message is:

Module IIS Web Core Notification Unknown Handler Not yet determined Error Code 0x80070032 Config Error The configuration section 'standardEndpoints' cannot be read because it is missing a section declaration
Config File \?\D:\root\web.config

Surprisingly, the access of the SUB app complains about the config of the ROOT app. Furthermore, the ROOT app config file contains a valid standardEndpoints section:

<standardEndpoints>
    <webHttpEndpoint>
        <standardEndpoint name="XXX.WebSite.WS.Program" helpEnabled="true" automaticFormatSelectionEnabled="true" />
    </webHttpEndpoint>
</standardEndpoints>

I don't really get why the the SUB application AppPool still checks the parent configuration.

Is there a way to 'break the inheritance'? Have IIS treat the 2 apps as completely separated?