dhcp clients not registering in reverse lookup zone?

DHCP server (10.0.0.100) dishing out the following IP config to clients:

IP range 10.0.0.101-10.0.0.254

GW 10.0.0.1

DNS 10.0.0.100 and 10.0.0.6

DNS domain name company.ads

There is a 0.0.10.in-addr.arpa reverse lookup zone on 10.0.0.100 and 10.0.0.6 that is AD-integrated.

I do see most clients in that zone.  But there are some that I don't.  I even did a ipconfig /registerdns on a few of them but to no avail.

The clients are a mixture of Win 7 Pro and XP Pro.  As I'm not in the office at this time of writing, I am not sure if this issue is isolated to 7 or XP clients.

Any ideas?