PXE won't get an address

Hi there,
I've been having a lot of trouble getting PXE to work and I really don't
know why. I have read through the setup documents and it looks like I have
everything configured correctly. All the required NLMs are loaded and my
clients are using network cards that fully support PXE booting. My server
is Netware 6.5 SP4a installed from the overlay ISO. I am running ZEN 7
Desktop Management with all services installed. The clients are using IBM
NetFinity 10/100 and Intel 8255x ethernet adapters flashed to their latest
Intel Boot Agent code and configured for PXE booting. The DHCP server is
setup on the same server as the PDHCP server so I have edited the PDHCP.ini
file according to the install instructions. When the clients boot to
Windows they successfully obtain an IP address provided by DHCP. However,
then the clients boot to PXE they time out trying to get an IP address from
the DHCP server. I have configured option 60 on my DHCP server and have
used the text string PXEClient as per the setup documents. Can anyone think
of something I may be missing or have any suggestions? Thanks for your
help, it is always appreciated.

Chris