Bought this router and I'm on Be* & I'm having the same issues. It just will not get any net activity what so ever, although it connects to the exchange like for the OP.
Spoke to one asus guy on phone and he said I would need to clone mac address from speedtouch to n55u, dunno how to do that... Another Asus guy said no need to do that as it's a modem router and ADSL, doing something like that would be for cable users..
Got it working with my other ISP (talktalk) but that uses PPoA with is pretty auto config after putting username passy in. BE* doesn't work like that though, as it uses IPoA and (static) IP address, gateway etc...
Arghhh it does stream 1080p stuff flawlessy though to the bedroom. Just wish I could use it with BE*
*sorry for bumping this thread, but it's on the same nature of issue as I'm having.