Can’t login to Site Admin right after installation

Hi, I’ve downloaded and now installed wordpress-2[1].0.4, using the 5 min Install (but looking at all the notes). I get to the third and final screen, that says all is done and provides the user name and password for the administrator.

But then it is impossible to log in. I get a HTTP 403 (Forbidden) error message saying “You are not authorized to view this page”. I have messed around in the database, to change password using MD5 hasher, and also deleted the database and re-installed the whole thing again. With the same problem. The home page can be seen without difficulty, but impossible to access Site Admin panel.

Any ideas how to solve please?