Cheers, guys. Turns out it's the other way around: I was accessing the internet via my neighbor's unprotected WiFi net. And it looks like he just came on too.
However, if I can see him, then he can prolly see me...!
But I don't think I can access him, or he me. Anyway, I've got everything buttoned down tight exactly for situations like this.
I'll quickly head back to my own net...