Clone/Duplicate WPMU site on same server

I'd like to clone/duplicate a WPMU site on the same server, but under a different directory.

The current site is like (using an example domain name here) http://site.com/wpmu and I need the same site duplicated under http://site.com/testwpmu.

What I've done:
1. Cloned the database to create a new database for the duplicate instance with a new database user and password.
2. Created a directory called /testwpmu/ and copied over all files from /wpmu/.
3. Edited wp-config.php under the new site, testwpmu, to point to the new database (with credentials) and also changed $base to '/testwpmu/'.
4. I also updated the wp_1_options table in the new database and set home, siteurl, path, etc., to point to the new path (http://site.com/testwpmu).

What I see:
1. When I visit http://site.com/testwpmu, I get redirected to the signup page for http://site.com/wpmu (the original site).

This doesn't seem like an Apache redirection from the rewrite logs. I've also tried defining WP_SITEURL and WP_HOME in wp-config.php. But it still goes back to the old blog's sign up page.

I have search the web and the forums, but I haven't seen anything about duplicating a site on the same server under a different directory without discarding the original site.

Any thoughts/suggestions?

Thanks!