Unable to access site via PWA

[M.E.]

We have a second instance setup on our IIS box, which I
can connect to via ProjectProfessional. I get the
following error when attempting to connect via PWA:

You are not authorized to view this page
HTTP Error 403 - Forbidden
Internet Explorer

We have Anonymous Access enabled, with IUSR_PMO00001 set
as the Windows User Account used to access the computer as
an anonymous user.

Any other setting suggestions?

thanks