I charge always my Motorola droid razr on original chargers suddenly from almost a full battery the phone shut and do not charge, the known M symbol stays on forever as long it's playground but don't charge and don't start

SOURCE: "Unauthorized Charger"

you can try to clean the charger port (but first make sure its not bent, or broken - the pins are really tiny and hard to see, so make sure)
But try cleaning the charge port on the phone and the charger with denatured (rubbing) alcohol, and a toothbrush -

Just make sure not to plug it in when you do this!

and clean both the charger and phone, make sure neither are bent
lastly, try a new charger!
NGK

SOURCE: Nokia N73 Music Edition Charges Forever

try factory reset ...... if that does not work get it checked with the nokia service center

SOURCE: BATTERY UNABLE TO CHARGE

shorting out battery

SOURCE: my motorola hint phone says "unauthorized charger"

u have to turn off ur phone and then put the charger on..thts another way to fix it ..it can be any charger..u have to turn off ur phone then put the charger on

SOURCE: my motorola razor says unable to charge bought new

I had the same problem trying to charge with one of those "universal" chargers. Then I find the original Motorola charger and that solved the problem.

I hope this helps!