Redhat 9.0 dhcp client & windows 2003 dhcp server: dynamic dns update

Hi,

I'm trying to add some linux (redhat 9.0, kernel 2.4.20-8) boxes to our
Windows 2003 domain.
The dhcp server is running fine, and the linux clients are getting leases.
However they are not
getting added to the dns forward lookup zone.

The dhcp server is set up to register *all* client leases in the dns, even
for those who do not request so.

The dns server is set up to allow both secure & insecure updates.

I've tried googling for a solution and have tried:
1) Adding DHCP_HOSTNAME & HOSTNAME to the /etc/sysconfig/network
configuration file.
2) Modifying the /etc/sysconfig/network-scripts/ifup script replacing
<snip>
if [ -n "${DYNCONFIG}" ]; then
PUMPARGS=$PUMPARGS
DHCPCDARGS="$DHCPCDARGS -n"
if [ -n "${DHCP_HOSTNAME}" ]; then
PUMPARGS="-h ${DHCP_HOSTNAME}"
DHCPCDARGS="-h ${DHCP_HOSTNAME}"
</snip>
with
<snip>
if [ -n "${DYNCONFIG}" ]; then
PUMPARGS=$PUMPARGS
DHCPCDARGS="$DHCPCDARGS -n"
if [ -n "${DHCP_HOSTNAME}" ]; then
PUMPARGS="--win-client-ident -h ${DHCP_HOSTNAME}"
DHCPCDARGS="-h ${DHCP_HOSTNAME}"
</snip>
3) Using redhats GUI network configuration tool to set the values - which I
believe more or less
amounts to 1).

Still no luck. If anyone has any suggestions I would be very thankful to
hear from them.

Regards

Mads Ravn