Yeah I have your answer, went through the same thing with wifey's w385. The phone won't accept other A/C chargers from other phones, even Motorola ones (like my Moto Q charger). Then I also encountered the issue with even the PC not charging it.
The solution is to simply reboot the phone after getting the "unauthorized charger" message. After that, it should charge normally again from the PC and its "authorized" charger.