I'm having the exact same problem. I recently moved home and the tehcnician replaced my router without me even considering that I needed to 'remove' the XFi pods from the old one. I can't activate the pods anymore and after several calls and hours with advanced technicians I've not been able to resolve it.
One technician claimed that there was a nation-wide outage for enabling pods but looking over the posts here it seems that someone needs to reset or de-register the pod serial numbers on Comcast's servers to properly reset them.
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