Hi guys. Hope you can help with my very similar problem.
I have about same configuration as above, however I'm not using a router, but an Internet Connection Sharing ad-hoc mode between 2 computers.
The host is running Windows XP and the client is the Acer laptop with the Atheros wifi.
I can see a list of wireless networks, I'm trying to connect to my home network but it is trying to connect for a few minutes, then it gives up.
I've tried all the things you mentioned here with no success.
Much appreciated any useful tip.