Then disable all security so everyone and their brothers can use it. Just be even quicker about it. That's what I had to do for my charmander and rufflet.
It can't connect because you're likely using a WPA connection. Try setting it to WEP for a little while you're trading or connecting to DS Wi-Fi. But it can be cracked in minutes and seconds, so make it quick. Change back to WPA when you're done with it to avoid any other cracking attempts.