Only dsis are compatible with wpa and wep security. ds and ds lite are only compatible with wep. i have the same problem as you, i have wpa, so if i try wifi at my house with a ds, it wont work, but since the dsi can access wpa and wep security, therefor it will work. Sorry for the long explanation :)
same with me. it wont detect it. in the wifi info book, it says that it should detect an access point. if the access point point have a gray lock, that means it is not compatible security. if you want wifi, you have to turn off security in order to do wifi or else there is no other way besides turning it off or changing the type of security you use.