NetworkManager failed to get a DHCP connect more than 50% of the time. One solution that seems to work is to get rid of NetworkManager and go back to the way it worked under Fedora 8.
1. Disable NetworkManager
# chkconfig NetworkManager off
# service NetworkManager stop
2. Change the eth0 interface so it is not managed by NetworkManager by deselecting "Controlled by Network Manager" in the properties of the eth0 interface in the system network config
3. Reboot and test