This system works well for remote distro upgrading Fedora Core 3 to 4 using yum.

rpm -Uvh http://download.fedora.redhat.com/pub/fedora/linux/core/4/i386/os/Fedora/RPMS/fedora-release-4-2.noarch.rpm

The kernel must be upgraded before the other packages.
yum -y update kernel

Disable SELinux:
edit file /etc/sysconfig/selinux
Change SELINUX=enforcing to disabled

reboot

yum remove kernel-2.6.\*FC3\*

rpm --import /etc/pki/rpm-gpg/RPM-GPG-KEY
yum -y upgrade

reboot again, upgrade complete.  Don't forget to reactivate SELinux.