[Ginto8]

Here's the method that's throwing the exception (from edu.wpi.first.wpilibj.networktables2.NetworkTableN ode):

	public void putValue(String name, Object value) throws IllegalArgumentException{
            if(value instanceof Double){
                    putValue(name, DefaultEntryTypes.DOUBLE, value);
            } else if (value instanceof String){
                    putValue(name, DefaultEntryTypes.STRING, value);
            } else if(value instanceof Boolean){
                    putValue(name, DefaultEntryTypes.BOOLEAN, value);
            } else if(value instanceof ComplexData){
                    putValue(name, ((ComplexData)value).getType(), value);
            } else if(value==null) {
                throw new NullPointerException("Cannot put a null value into networktables");
            } else {
                throw new IllegalArgumentException("Invalid Type");
            }
	}

NetworkTables can only contain Doubles, Strings, Booleans, and ComplexData. ComplexData is implemented by ArrayData, which is extended by BooleanArray, StringArray, and NumberArray. I think you want to use NumberArray, and as far as I can tell, you'd use it like this:

NumberArray outputArray = new NumberArray();
outputArray.add(double1);
outputArray.add(double2);
networkTable.putValue("array",outputArray);