Mooney has let us know, that sgtair has updated his WiFi Library for the Nintendo DS. The release notes for this release:

Ok, an update for those of you who were stuck on ASSOCSTATUS_ASSOCIATING for the longest time… (version 0.2a [wifi_lib_test.nds]) Firstly, the new build spoofs it’s rate set (pretends to support things it can’t) in order to properly associate to APs that don’t have a low enough base rate set. Also, there have been a few other bugfixes (fixed a crash bug, on ARP timeout) What this means for you? People stuck on ASSOCSTATUS_ASSOCIATING will probably be able to connect now!, and in the case you can’t associate, it’ll tell you much sooner. Also, a note (this wasn’t gone over before) – WEP does not work in this version (also, wep has nothing to do with association, so you’ll be able to associate, just not do anything) – I’m working on it and trying to figure out what’s wrong though… More to come, whenever.

http://www.akkit.org/dswifi/index.html