IntraWeb ISAPI Module throws “Unrecognized Command” Error on IIS 7

Question

I am trying to configure an IIS7 web server to run my IntraWeb 10 application. I followed the steps described by Dr. Bob and Chau Chee Yang.

The application starts but results in an error: Unrecognized Command: : WEB:.

(Web seems to be the name of the virtual directory used - I tried different ones and the message changes corresponding to that).

Looks like the virtual directories name is passed as a parameter to the ISAPI DLL...

The same DLL runs nicely on a web server with an older IIS (6 i guess).

Is there a configuration option that could cause/remove this?