I am having a similar problem to the original poster (continuous redirects to /wp-admin/&reauth=1). My server timed out during an upgrade from 2.9.2 to 3.0.1 using the WPAU plugin and never completed some procedure.
My website is waitiki7.com; the admin panel should be located at waitiki7.com/W7/wp-admin; and my host is ApolloHosting, running PHP 5.2.12 and MySQL 5.0.45. [I cross-posted this to How To/Troubleshooting since this installation runs only one site and is therefore not necessarily a multisite problem.]
So far I have done the following things:
1. Backed up
2. Replaced core files—completely deleting old ones before uploading the new (3.0.1)
3. Deactivated plugins folder
4. CHMOD’d /wp-admin/, /wp-content/, and /wp-includes/ to 755
5. Deleted my .htaccess file
6. Cleared my browser caches…
7. Going into phpMyAdmin to verifying that siteurl within the MySQL table wp_options is correct. (It was)
8. Adding the lines
update_option('siteurl','https://waitiki7.com/W7');
update_option('home','https://waitiki7.com/');
to wp-config.php —nothing happened, so I deleted them again.
9. Deleted install.php from the /wp-admin/ directory.
Any suggestions or help would be greatly appreciated. I’ve been reading forums for hours now and have not come across a solution.
Many, many thanks in advance.