Description of Problem: During the installation configuration, if you uncheck Active on boot for a single NIC install, the areas for entering the gateway and dns ip addresses are greyed out. It should be possible to set these values so everything is setup to run after the install and runs after ifup eth0 is executed. There are situations where you do not want the interface automatically brought up on boot. I do not expect this to be fixed until the net release.
In the current code, these are settable if you are not using DHCP. If you're using DHCP, then they'll get overriden by your DHCP settings (and they make no sense before the interface is brought up)