Probably the output on the previous charger is not adequate for your Lumia to start.
The Nokia E6 have an 1500mAh, thus it needs a more powerful charger so it will charge faster, which Nokia have provided. (Says it has an output of 1300mA in an hour). If I remember well, the charger that comes with the Lumia 800 has an output of 1000mAh.
But then, that was just my assumption and it's not totally right.