RE: USB. As far as I know, the Wii does not support a USB-LAN connection. Yes, you can buy a USB-Ethernet adapter, that's not what I'm talking about.
RE: SSID. Enter the SSID as TEXT, not ASCII/Hex. Stick with Alpha/Numeric/Upper-Lower Case. Also, if your router supports WPA, use that not WEP as WEP can be cracked by any script kiddie in about 2 minutes with a laptop. The MAC address can be found on one of the Settings/Internet screens, look around a bit.