Every time it does that, it's a mutual thing. It's not fixable by restarting the wifi/flipping the switch on and off. I have had that issue with a couple of people in the past. It's a weird connection thing -- I trade with one person, and then the next can't connect to my DS. I think it depends on location.
That's weird indeed o:
I never had that hehe. &idk with the location.. I'm in europe and I traded with people over the whole world.
Well I hope it goes well with the next person =]