I know that many of the php files have relative paths to other php files in the /wp_includes/wp-admin/wp-content directories. This was the problem I first had trying to install V2.7.1. The install failed because, even though I had the files in the root directory, it was looking for a sub directory. Once I uploaded that structure it worked fine. My only problem now is that I want to upgrade to the latest version and the zip doesn’t seem to have that structure.