I'm having the same problem: just can't log in as admin.
Install worked fine, and when I tried to log as admin with the password it gave me, just didn't move. If I try to log in as admin with a wrong password, it advices me, but if I write the correct one it just get "hanged", waiting and waiting but with no results.
Sometimes I even can't use wp-login.php or wp-admin (hang too), whereas other pages work. Tried to upload and reinstall the blog form zero, but also didn't work.
The server run:
Php 4.3.10 (safemode on , register globals off)
Wordpress 1.5 - Strayhorn (downloaded yesterday from the official link)
Any idea of what can be wrong?