For clarification, have you only installed the PC part of it, and nothing new on the BB? Where does 4.0 get installed? PC? BB? Both?
Again, guessing here, but the closest example I'm thinking of is a USB cable or DSL modem. Just plug it in and it "finds" the network/internet. A quick test would be to determine the address of the BB and ping it. You probably have to go to a dos prompt to do that. Not sure about XP.
Once you figure that error on the BB side out, and if it still doesn't work, I wonder if rebooting the PC would help reset IP address. I don't know how to release/renew IP addresses of USB ports - or if you even need to.