Just to clarify, MAC address is not IP Address. The Mac Address is fixed to the computer and does not depend on where you connect to the internet. It only depends on "which connection" you use - Wireless or Hard Wired.
I will admit it is a bit of a pain if you always connect "both ways" at various times. I would like to see Web Assist silently increase the "activation limit to 3". That would be a very quick fix for this as that would not need any new programming on their end.