What are you using? If you are using a EMU then you can make one up. See the below link. If it is a Mag then you need to take a picture show your MAC and send that in to get it reset.
hxxp://www.hellion.org.uk/cgi-bin/randmac.pl?scope=global&oui=00%3A1A%3A78&type=mult icast. Replace xx with tt.
i Had The Same Problem... Turns Out Opera Kept Blocking The Request... I Used A Different Browser And It Update No Problem.... I Used One Called Black Hawk Web Browser.... Others May Work As Well...... Good Luck..