Here is instructions for the BT Voyager 2100 which is not the identical model so you'll have to see yourself whether it fits or not. 1st you must set up a static ip for this to work. Then you can forward a port (ie: open port 6346 for LW to have full access.): http://www.portforward.com/btvoyager/2100.htm

I'm not sure whether your modem uses UPnP so if you still have connection problems after that I'd suggest you try manual Force ip within LW: Force IP instructions & sample image (& also 2 post after that!) Of course use Port 6346 for all port forwarding & force ip.