Have you tried multiple Wii Remotes?
Have you recently put any glass or any strong light sources in between, near, or even in the same room in general (I know the question was asked before, just makin' sure)? They can interfere with the Wii's Infrared.
Are the batteries for your Wii Remote dieing? This is probably the problem only if your Wii remote's cursor is blinking/flashing. But even if it's not flashing, best to check anyways.
Since you've even tried a different sensor bar, so long as your warranty is still in check, I don't see why it wouldn't be covered.