I have a WPMU installation, which I have just upgraded to WP3.0. I have multiple domains using the same installation but *some* of the non-primary domains are broken with the above error displayed instead of [anything!].
I've tried messing about with plugins, even disabling them through the database - no change.
I used the automatic upgrade on the primary domain (main.com). All of the blogs, er, sorry, "sites", on this domain work fine, e.g. main.com/bloga, main.com/blogz.
In the dashboard of the main.com sites, "my sites" displays all of the sites across the entire installation. In the super admin "sites" menu, only the sites in the current domain (main.com, sub1.com) are shown. This seems backawrds to me?
Anyway, any ideas what to try next please?