WP 3.0 Blog Posts Redirect Problem

I upgraded to 3.0 and the blog post links are no longer working. The message is that “The page isn’t redirecting properly. Firefox has detected that the server is redirecting the request for this address in a way that will never complete. This problem can sometimes be caused by disabling or refusing to accept cookies.”

I have tried a re-install, once I’ve disabled all plug-ins and used the 2010 template. I made no other changes; upgraded all last year with no problems at all.

I did back up my wp-admin, wp-content, and wp-includes, .hcc.thumbs, plus did a basic Export before upgrading.

So 1) is there way to fix this in 3.0 and if not 2) is there a way for me to roll-back to the older version given what I backed up?