Tetris DS, Mario Kart: wi-fi connection

Hello. This is my first post. Everyone on this forum seems really friendly and helpful. I hope I can also be helpful to you in the future.Here is my problem. When I select Wi-Fi BATTLE in Tetris or Mario Kart it tells me I have no compatible access point in range (53100). I can access Nintendo Wi-Fi Connection with Pokémon games. I can also browse the internet... etcI'm probably doing something wrong but I can't figure out what...I am using a clean ROM which I downloaded off this site a while ago. I am running akAIO 1.7. My d-link router uses WEP.This topic from last year seems to outline a similar problem...
http://forum.romulation.net/index.php?topic=19289.0

I think it's because your internet is WPA it needs to be WEP.
You can change it but WEP is not as safe. I have WPA.

Sane here. You have to go to a website, it should say on the box of your router, and change the security settings from WPA to WEP. It gets very annoying though.