I am new to the Wii scene but I have a similar issue but it has happened to two consecutives Wiis in short succession, both while playing gamecube games via nintendont... I have a third Wii on the way to see if it happens again...
sorry, beein trying to find this file that's been right in front of me for a month now, only to find broken links, and google to prove that it's completely worthless.