I have the same issue. Just happened yesterday. Turned off the phone to charge it overnight. As soon as I plugged in the charger, the LED was flashing green/yellow.
Usually when I charge it, the LED lights solid RED. This flashing LED is not normal.
When it's off and charging the led should flash green/yellow until it's charged, then solid green. There's no red going on in the charging deal. Red's for messages, yellow's for low battery, blue's for <dromroll.................>