Nintendo 3DS not connecting during online games to Macbook Pro or Airport Express Network. Please Help.

I would love to post this question to the Nintendo Support forums, but I'm abroad right now and it seems I am denied from the forums if I try to log in.

My Nintendo 3DS's internet features all work perfectly fine except when it comes down to directly playing a match with other users. For example, Mario Kart 7 will download Spot pass data like normal every day, but everytime I tray to play a match online, the software gives me an error. Same thing when I try to connect with people on Animal Crossing: New Leaf. My previous linksys router back in the states worked fine. The security was WEP I remember. Now I've got myself an Airport express and neither it nor my Macbook Pro (when sharing is turned on) will permit me direct online access to other users like I stated above. I even disabled security and went with an open network for a few minutes and was faced with the same exact problem.

I know this is very specific and mainly involves a none apple product, but I'm just curious what is different about the Apple wireless networks I'm setting up that is preventing me from nothing but direct realtime interactions with other users.

Any advice or knowledge about Apple security or wireless networks would really help me out. There are only so many settings I can tweak in the Airport Express so I'm sure it can't be too difficult, but I don't even know where to start.