I have been facing this issue for a few hours now. I have looked through the forum posts on this topic to no avail.
back ground on the site. did a manual upgrade after a suspected automatic upgrade was assumed failed. spent 4~hours fixing that. got logged in that day and reactivated my plugins. this was Friday(01/15/2010). have not touched hte site from then once it was back up. went to log in today and the site was throwing a 404 error when attempting to log in.
login should be at= http://prhstaugustine.org/blog/wp-admin
running wp 2.9.1
have tried renaming the plug-in dir and nothing changed
re uploaded the wp-login.php and nothing changed
the login link is at the bottom under the footer