assuming it's not the overheat issue, which should be obvious as the charge indicator (lightning bolt) won't show...
check the battery stats while on the charger. is should show either 'charging usb' or 'charging ac'.
if it says usb, it will only draw 500mA current max, in order to be a good neighbor on what it thinks is a shared usb bus, potentially with other devices. this is not enough to power gps/3g data simultaneously.
if it says ac, then it will try to draw the current that it needs and your charger is incapable of providing it. look at the fine print on the charger? what does the output current show? i used a micro-usb charger from another phone that was rated at 750mA and had the same problem you describe. i got a usb vehicle adapter from radio shack rated at 1000mA, which the phone sees as AC and which (slowly) charges the phone even with bluetooth/gps/3g running simultaneously.