I started off with 3.1 RC4 and set up a multisite setup. I was able to do things properly. I could get to the dashboard of all the sites that I've created. But now since I've upgraded to final version of 3.1, I can't log in to any other site, except for the main site. When I click on the dashboard of any other setup, I get taken to the login screen. I try to log in, but it doesn't go anywhere.
But I can still log back in to the main domain.
So I can do everything, and see everything in the back end, just as long as I don't go to try and manage another site in my setup.
And like I said, it was working fine when it was 3.1 RC4, but the final 3.1 broke it.