Error when not uploading a sketch

Hi there! :slight_smile:
I have my arduino sketch working among an arduino ethernet shield. When i simply connect my arduino to my computer and upload the sketch, it works fine.
However, if i only connect my arduino without uploading the sketch, it doesn't work fine at all.
I have set up a led to blink at the begining of the program to be sure that the sketch is well saved on the Arduino. It appears that the led blinks correctly but the software seems to stop working when the sketch starts to initiate the ethernet connexion..
I don't really understand that problem as it works perfeclty when the sketch is uploaded and simply not working when i just switch on the arduino ..

Any ideas ?

Thanks in advance,

Quentin :slight_smile:

What happens if you connect without uploading, then press the Arduino's reset button?