If the RedHat mirror is stored in the root of the anonymous ftp server (which is quiet uncommon), the installation will hang. The reason is that the installation script runs the following command on the FTP server: "CWD ". In this case, CWD takes no argument because the mirror is in the root, but unfortunately, the scripts adds a space after CWD, so the command is not understood by the FTP server (wu-ftpd-2.6.0-3). Then the scripts loops indefinitely, and the installation won't happen.
This is a bug in python's ftp module, which we should fix eventually.
Fixed in RH 7