Problems with DHCP in F7 kickstart

[Bevis R W King]

I'm currently trying to get Fedora 7 (F7) to kickstart a PC.  I've tried
various kickstart files, but the one I've settled on is an
anaconda-ks.cfg created by a manual workstation install via HTTP on that
very machine.

If it contains the line:
network --device eth0 --bootproto=static --ip=131.227.95.104
--netmask=255.255.255.0 --gateway=131.227.95.1 --nameserver=131.227.76.3
--hostname=willow.eps.surrey.ac.uk

it works.  The workstation then installs perfectly.

If it contains the line:
network --device eth0 --noipv6 --bootproto dhcp --gateway 131.227.95.1
--nameserver=131.227.76.3 --netmask=0xffffff00 --onboot=yes

It doesn't.

Silly thing is after getting the initial boot menu, hitting <TAB>,
adding " ks" to the boot string and hitting return, the machine DHCP's
for it's address successfully, gets the ks file and goes after the
correct HTTP-based install repos.  It then calls getNetConfig, I assume
as a result of the above directives, sends on the the DHCPDISCOVER calls
and after about five attempts, fails to get the DHCPv4 address it was
given before.  

The syslog on the DHCP server indicates that a DHCPOFFER is being sent
each time.

The console 3 log says:

INFO    : DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 17
INFO    : DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 17
INFO    : DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 7
INFO    : DHCPv4 eth0 - TIMED OUT.
INFO    : doing kickstart... setting it up
ERROR   : no DNS servers, can't look up hostname
INFO    : starting to STEP_URL

and then fails to get stage2. 

The DHCP server in question worked fine for dynamic assignment in FC6,
and has all the options configured for that - dns-servers, etc, etc.

Any thoughts on what might be causing this?

Regards, Bevis.