During the bit where you configure the network cards in the GTK interface,
deselecting "Activate on boot" causes "Configure via DHCP" to become disabled.
"Manual" becomes selected, being the only option left.  It didn't complain that
I didn't enter an IP address or nameserver though.

Version-Release number of selected component (if applicable):
FC5

How reproducible:
Only tried it the once.

Steps to Reproduce:
1. Go through the FC5 installer until you get to the screen where you configure
your network cards.
2. Deselect "Activate on boot"

Additional info:
I seem to recall that you could go into a more detailed configuration screen and
that there was a similar problem in there.  Unfortunatly I was scribbling and I
can't read my own writing :(

Also, I don't know if this matters, but I was doing a NFS install so the card
was already active at this point.