I just upgraded from 2.0.7 to 2.1. The theme I was using was working perfect in 2.0.7. I uploaded all the 2.1 files except wp-content, over-written the exiting ones. The process went fine but when I went to my index page it gave me the "Not Found" - Search Results page. I see all my entries listed under categories, etc. I even put in a new post which can be seen on the feed but not the actual page. When I click the permalinks for a post I get the "Sorry, no posts matched your criteria."
I applied other themes to my blog and they all work fine with it. The only thing I can think of was the theme was activated when I upgraded. I tried copying the theme and upgrading under a different theme name but I got the same problem. Anyone have any idea?