Something that has bothered me for a long time was that I could never get my DS to connect to my home wireless network, via Airport Extreme. The issue is with the newer model Extremes that operate at 802.11n and the DS's very picky DNS and security protocols. Nintendo's tech support on the subject is outdated, and I have visited random boards over time trying to find an answer but none ever worked for me. I even asked at the Apple Store and they had nothing to offer, but were oddly interested in wether or not the issue was on Nintendo's side or AirPort's side (might have something to do with recent Safari hacking shenanigans). alas, no setups or manual configs have helped-- UNTIL NOW!
Recent google searching brought me to this post wherein a key feature of AirPort Utility 5.3.1 was revealed!
Wrt getting the Nintendo DS to work with the new Airport Extreme base station 802.11n, the following article provided me the critical hint: Use Option (Ctrl on WinXP) when selecting the radio mode, more choices will appear. I selected "802.11b/g compatible", then I selected WEP 128 bits, entered a 13-character sequence, and bingo. The NDS saw my network, I entered the same 13 characters on the NDS, and I had a connection. (link)
While the article link he referred to was dead, that small tidbit about using the option key for additional items in the pulldown menus was TRUE. Sure enough the extended settings allowed me to access my home network from my DS. WOOT!
Thank you, mystery forum poster, for helping me finally get online -- at home -- with my DS.