After upgrade to 3.1.1 going to the network update on wp-admin/network causes a redirect loop.
In wp-config.php I have:
define( 'DOMAIN_CURRENT_SITE', 'www.example.com' );
If I change it to:
define( 'DOMAIN_CURRENT_SITE', example.com' );
It works, which I did to do the network upgrade. But then I noticed my permalinks weren't working properly (a link to a post would take me to the front page). So I updated my permalinks and everything works properly. But because I'd edited my permalinks on the main site to not include '/blog' at the start I needed to take that out again - which brings back the redirect loop.
So I've put the 'www.' back into the DOMAIN_CURRENT_SITE which makes it work from the site users' point of view but I can't access my network admin.
I'm kinda going round in circles with this.