Portal 7.3 not working through NWBC 4.0

Hi

Installed NWBC 4.0.

Tried to open Portal 7.3 through NWBC.

Got the Logon Page.After Logging in got the Following Error.

Could not open the logon window for the server with the supplied URL.

Check that the URL is valid and server is running.To do this, call the same URL in the browser.

The URL Works fine in Browser.

Portal 7.0 works fine in NWBC. Any Clues?

Regards