Accessory no longer charges iPhone

I have been using a Logitech Pure-Fi Anywhere 2 speaker system as a charging station for my iPhone 3Gs for the last year or two. Suddenly, now when I plug my iPhone into it, I get a yellow triangle and an error message saying that "Charging is not supported with this accessory." Why would it suddenly stop charging my iPhone when I've been doing it for years? Any way to remedy the situation?