I've had a quick scoot around the internets, and I think you're right. My lil computer (it's a nettop) has an Atheros AR5007EG wifi adapter inside it. Despite Play.com (and other sites that sold the machine at the time) saying it was capable of G & N, it seems that isn't the case. So it looks like I'll have to keep it wired into the hub (which is hardly the end of the world, as the hub sits around 30cm away from the computer
).
Cheers for the help