Blank/hidden login form.

Hello,
I've just installed opmanager on a windows 2003 server.

When I try to access to log-in page I get an "empty" page.
I've tried with:
- firefox(linux);
- firefox(windows xp);
- ie(windows xp);
- ie(windows 2003 server);
- opera(linux).
Always with the same result: the "empty" page.

I write "empty" because, using the "Show hidden elements" function in firefox (thanks to WebDeveloper extension) I can see the login page (just a little deformed) and then correctly log-in and use opmanager.

I've searched into forum but I've found no solution.

Thanks,
matteo