Hawhill, thanks for your post (and your hack).
I tried pinging my DX via putty, but I couldn't get a response. (My puttytell simply will show the code that I've typed -- "ping 192.168.2.2" -- then it close after 8/9 seconds, as usual.)
I don't believe that I'm on a private WLAN. I just use standard password protected 801.11 wifi network. Also, I have no idea why Tightvnc shows two different listening ip adresses (Ultravnc does the same thing). About 8 months ago, when I was first messing with the kindlevncviewer hack, my computer would recognize my DX as different RDNIS device (and install new drivers each time) the first few times that I attached it to my computer using the usbNetwork hack. My computer eventually stopped doing this, but afterwards Tightvnc was always shown two ip addresses. (Also, in the past, I have been able to use the kindlevncviewer hack even when two ip addresses were displayed by tightvc.)
I have read the documentation associated with both the kindlevncviwer and usbnetwork hacks. I have not changed either hacks' default settings.