lol since I didn't specify I thought it was implied that I was referring to the guide you wrote in the previous page. maybe I should have said it...
I did everything exactly as you did. I'll try to redo everything from scratch.
I have windows 7 and my wifi card is a qualcomm atheros AR9285. I updated the drivers before trying the guide.
I don't know what else to tell you since I have done really everything the same way you did. the screenshots would look the same.
edit: I found something. the mac address of attwifi is 2E:53:50:4F:4F:4C instead of 4E:53:50:4F:4F:4C, that is the one I put with macshift. I don't think this should prevent the 3ds from connecting, anyway.