> Could not retrieve mirrorlist
> http://mirrors.fedoraproject.org/mirrorlist?repo=fedora-10&arch=i386
> error was
> [Errno 4] IOError: <urlopen error nonnumeric port: 'port'>
> Error: Cannot find a valid baseurl for repo: fedora

This may be a dumb question, but did you verify that you can access that
url say in a web browser? I can confirm that it is a valid URL and I
could open it in firefox. If you can't open it, then you likely need to
check your internet or firewall settings.