Wii Error Code 51000-51099 - Wii Error Codes

This error is caused by an unspecified issue.
To solve this error :

Try changing the channel of your wireless router to either channel 1 or channel 11 which can increase download speeds. Be sure to test both channels to see which works better or faster.
Set broadcast settings on your router to "Mixed." This usually produces the best results. If not, trying setting your router to "G" or "B" to test which works best.
Disable any nearby wireless devices, such as wireless keyboards and mice, that may be causing interference.
The Wii could be unable to connect to Nintendo's servers.
Please wait and try again.