I experienced the same problem when I attempted to install XOOPS on my Fedora box. I had initially used the mv command to move all the files from the htdocs directory in the XOOPS package to my server's document root. Attempting to access any of those files would result in an access denied error (even the css file).

The solution for me ended up being to copy the files (using cp) rather than move them. I can not offer any information as to why this would fix the issue as ownership and permissions are exactly the same as when the files were moved, but it seemed to be the solution for me.

Hope this helps.