Virtual machine. I'd suggest you check the network connections between the virtual machine & main machine. I also run a few virtual windows but do it on a mac. You suggested you had been able to run LW 4 but on a different virtual machine on the network. The fact you cannot access that test page probably means all ports above those that a browser uses are blocked. These network settings are either in the virtual machine program setup or within your main machine settings, maybe both. I had to allow firewall exception for the networking with the virtual machine on my main machine. I also have different network addresses set for each virtual machine.
Also, for Windows XP firewall, go to firewall exceptions & add LW. Also check the box to allow UPnP.
Another issue, LW on one machine cannot use same port to connect & listen through as any other machine. The router will block them.
The Westell in my experience are best port forwarded, however if UPnP has worked for you in the past this should be ok with luck. First check the main network settings between the virtual & main machine.
I presume you can at least use your browser on the virtual machine?