Macintosh OS X not receiving Windows 2000 DHCP reservation

I have a pool of Mac OS X machines that I would like to assign reserved addresses from a Windows 2000 DHCP pool.
This does not seem to work on the Macs (works fine with all x86 machines).
Can anyone tell me if there is known problems with Mac DHCP reservations, or whether it should work.
I’m suspecting that there is a DHCP client comliance issue, but I’d like confirmation so I know how to move ahead on this.