Why can't I change this MAC address under Vista?

For some reason, Windows Vista (Ultimate 6.0.6000) is not letting me
change the MAC address of a D-Link DWL-G510 wireless PCI adapter.

If I make the change, reboot, and bring up the adapter Properties
(through Device Manager), click on Advanced, and select Network Address,
it does still show the value as being selected and set to the changed
MAC address.

Also, if I use Regedit to go to:

> HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Contro l\Class\{4D36E972-E325-11CE-BFC1-08002bE10318}

and then to the adapter's subkey under there, the appropriate
"NetworkAddress" string value is set to the changed MAC address.

However, when I execute "IPCONFIG /ALL" the Physical Address shown is
still the real hardware MAC address.

I even tried logging in as "Administrator" and see the exact same thing
there. The Registry and adapter properties show the changed MAC
address, but IPCONFIG (and my router's DHCP client table) still show the
original physical address is being used.

This is a dual boot system and I can change the same adapter's MAC under
XP, so this must be a Vista specific problem.

Even stranger, there is another adapter built-in to the motherboard and
I can change that MAC address under Vista without any problems. It's
just the D-Link adapter that a change doesn't take effect on.

I've also tried various release/flush/renew, reboot, and power cycle
combos without any success and there are no MAC address conflicts.

Any ideas? Is there some trick I'm missing?