As the error state, you are using somewhere an object that has more than one property with the same name . Something like :
var obj= {
property1: 0,
property2: 1,
property1: 2
};
Printing the upper object results in :
{ property1: 2, property2: 1 }
Also searching a little bit on stack overflow, you can find a more detailed answer why this error is outputed in Internet Explorer