I just installed 2.7 on an ip. When I logged into the admin it was REAAALY slow, and on the bottom of the page I got the following errors:
Warning: ksort() expects parameter 1 to be array, null given in /home/websaum/public_html/wp-admin/includes/mu.php on line 740
Warning: Invalid argument supplied for foreach() in /home/websaum/public_html/wp-admin/includes/mu.php on line 741
I searched but didn't find any relevant support information.