I've had my Wii since launch. Since about 15 minutes after launch, I've had the same two remotes synced to it. Last night, in the middle of use (navigating the channels screen, nothing intense), the remote I was using just stopped responding. The batteries were fine, probably replaced a few weeks ago actually. Regardless of what button I pushed, all four blue LEDs on the remote would flash together.
So, I tried to resync the remote and had no response. Deciding to worry about it later, I grabbed remote 2. Same thing. Wouldn't respond to a sync either. I've gone through the online troubleshooting and, after having done everything Big N suggests, they recommend that I may have to ship the console to them for repair. Not something I'm terribly excited about having to do.
Has this happened to anyone else, and if so, what was the outcome?