You'll get that if you have "custom mac" enabled in Portal2, but not correctly formatting it. It has to be in this format: 00:1A:79:xx:xx:xx
where x's are hexadecimal characters.
If you are using a custom serial number, you should also configure the device ids and the signature as well, because if you don't, IPTV Stalker will error out.
@irish girl, what are you trying to do? I know you've gotten some help in the past, on the PVR Stalker, but unless you are just curious about IPTV Stalker, it has limited functionality as compared to the PVR. I recommend that most people stick to what works for them, unless you enjoy the pain of running into authentication issues by running different "stalker" client add-ons.