I think that while the 2nd server was enabled, NLB was doing its job correctly and trying to route all newcomers to it because it was the least busy machine. So I suspect that there's an IIS configuration problem on that machine that's preventing it from working.
I've disabled the internet connection on that machine via Control Panel, but left the cable plugged in. If it works this way and the 1st server starts catching all the traffic, anything else should be do-able from home.