no it's just that with the stb you have to provision every new pc that you use (as you know)
not quite the same with cable modems there is no provisioning for each individual pc the only thing that needs to be registered is the mac of the cable modem on the address that you mentioned
the problem that voodoodan will have probably is that the cable modem is already registered on the system,
and if it is not the reg page would not work because his pin is already registered