This error is caused by the Wii being unable to connect to the access point.
To solve this error :
Try changing the channel of your wireless router to either channel 1 or channel 11 which can increase download speeds.
If your router is using WEP encryption
Ensure your key is hexadecimal, consisting of 0-9 or A-F only, no other special characters or letters.
64 bit encryption requires your WEP key to be 10 characters consisting of numbers or leters A through F.
128 bit encryption requires your WEP key to be 26 characters consisting of numbers or leters A through F.
If your router is using WPA encryption, the Wii is compatible with :
WPA - PSK(TKIP)
WPA - PSK(AES)
WPA2 - PSK(AES)
If your router is using MAC filtering, ensure the Wii MAC address has been added to the list of approved MAC address on your wireless router settings.