I wonder if the Mu and your plug have the same complicated insides as an Apple iPhone charger. This article was recently posted here: http://www.arcfn.com/2012/05/apple-iphone-charger-teardown-q...
http://www.arcfn.com/2012/03/inside-cheap-phone-charger-and-why-you.html
http://news.ycombinator.com/item?id=3903705