None of the pages work after upgrading from 2.3 to 2.5.
I did a var_dump of the $_post variablein get_post() function and it is able to find a post. But it still says on the page that no posts found. It doesn't work with permalinks as I found in a post on these forums. You also need the preview=true.
My permalink is: /index.php/%postname%/
I couldn't find a bug submission page so I'm posting here.