i had this error and got mine and a friends working this way
total manual setup
on the router - add and allow MAC address of Wii, reserve an IP for Wii, DMZ the Wii's IP (this is my only wireless device so i don't use encryption- heh encryption for my Wii packets !!)
on the Wii - find access point , select it , done
thats it, so easy!!! at least for me....