Tried registering it over the phone yesterday, no luck. The globe light just keeps blinking. Was told someone from Tier 2 support would call, but they never did.
I found a few other threads in the forum suggesting that this model has an issue with Comcast's IPv6 protocol or something like that, and that it's a known issue which can be fixed easily on Comcast's end. If there's a Comcast employee here who could help, let me know and I'll PM you the MAC and S/N.
Thanks