Relocating WPMU

I am trying to move my WPMU installation from one hosting company to another, but the new install gets caught in an infinite loop.

(1) I copied my site files and exported my database.
(2) I uploaded the files to my new host, created a database and imported the MySql..
(3) I edited the wp-config.php to reflect the new database password and user and the new server.

When I try to navigate to the domain, I am redirected in an infinite loop. The URI indicates that the script is trying to redirect me to wp-signup.php.

I have disabled each of the following in turn ... index.php, .htaccess and MySql.

The error appears to be related to something in the database.

Can anyone advise me either what to change, or a process to follow for migrating from one server to another?