Interestingly, using your above code this also returns an empty string, with GetIPOptions, when discovering the MAC address of the Wireless Adaptor. It's not empty when using EnumNetworkConnections.
Example output:-

Connection Name: Wireless Network Connection 2
MACAddress: 00:13:02:CA:6A:B7
Adapter Name: Intel(R) PRO/Wireless 3945ABG Network Connection #2
Mac Address:
Static Address:
DHCP Enabled:
IPaddress/SM:
IPaddress0/SM:
IPaddress1/SM:
IPaddress2/SM:
IPaddress3/SM:
DefaultGW:
DNS Servers:
WINS Servers:
DNSSuffix:
DNS Search Order:
DHCP Server:
DHCP Lease Obtained:

Happy Xmas,
Bill
_________________________
Bill