Update: Having BE allocate and me configure a static IP makes the connection work.

This does appear to be a DHCP problem on the WAN.

Do Be still do something funky with regard to the original MAC address of your Bebox? IIRC you used to have to clone/spoof the Bebox MAC on any other routers or wait x hours for the Be network to register the new router MAC?

edit: 40 minute downtime mentioned here http://beusergroup.co.uk/technotes/index.php/Bebox_Alternatives