May I ask which model of Westell Wirespeed (it should have a model number)? Reason I ask is Westell modems & routers do not utilise UPnP at all well. And not all Westell devices that have NAT abilities even have UPnP implementation.

Which model of Bufalo router?

I suggest starting here:
1. You will have Vista's firewall on your computer, make sure LW is allowed in it's firewall rules. Setting up an exception for LimeWire in your software firewall (click in link). If it's already listed, you may need to remove that firewall rule & add a fresh one. Perhaps the old LW listing is not applicable to the newer LW 5 version whilst it's using Java 6 (1.6).

2. If LW Will Not Connect (click on the blue link)