A friend of mine had the same problem with is x4 charger. Turns out he shorted the battery cable when he used one of those octopus cables. With battery attached and a short generated, it overloads the Mofset that shuts off the power from the charger to the battery when the charge is complete. The Mosfet cant handle the power surging through the short and it burns up. Visibly its hard to see but if you look closely, it is broken.
This is the Mosfet in question:
http://www.alldatasheet.com/view.jsp?Searchword=F7413
I ordered up a few and swapped it out. Works great now.
This is not to say this is the cause of your problem, or even the solution to your problem, but it may be worth a look.