I finally broke and replaced my Vista-incompatible wireless router with a new Belkin model. A bit of muttering and swearing at the blasted thing when it refused to connect to the internet revealed that I'd typed in my username wrong and after that it was all plain sailing. My old XP box also hooked up to the new router problem free.
Surprisingly the new connectivity hasn't had too much impact on my writing routine- I guess that period of enforced no-internet-access has given me some good habits. Hopefully the new home network will allow me to get back to doing the occasional blog post.