@vague rant: i also have a netgear router and wifi is working perfectly. my settings are channel 11, 802.11b and g mode, range enhancing feature turned off, ssid set to public broadcast with a valid ssid, 128 wep encyption, my SPI firewall is off (because it turns off port forward rules for no reason which annoys me on IRC), MAC filtering is turned on with the nds entered. i let my ds obtain the link through the firmware automatically had never set anything by hand. wifi functions on my m3 lite, r4, akrpg, ak2.1 green pcb, and ak2.1 black pcb.
if homebrew isn't working but retail dumps do, then the problem is with the router. the cart is not selective which is allows (besides from the obvious roms that fail and are known per cart). keep toying with it!!
i've noticed with my own set up that sometimes sitting right in the room i can not get a signal. so i will hook up a retail game that works (like zelda), let it connect, then softreset or shut down my nds and do the homebrew. i don't know if the data tables in the router require the IP of my nds before they let wifi in sometimes. the thing only cost $75 so i never expect perfection out of it. also sometimes simply hitting the "apply" button in the wifi settings to update the router and rebroadcast has allowed me to get online. finally i can sometimes connect when i'm 2 feet away but not right infront of the router. try holding your nds up or away from the router if you are sitting directly infront of it.
goodluck.
-another world