Funny things happening with Arduino cards

Development Tools IDE 1.x
1

Looking at the card USB port to the left for reference.

I have a sketch running. Pin 0, 1, 2, 3, 4 are used. 0 being the top RIGHT pin and then counting up going to the left.

I modify the sketch and try to upload. It won't. I have to disconnect the power to the external circuit before I can update the Arduino.

So if I move the outputs to 3, 4, 5, 6, 7 I can update the Arduino ok.

So I would seem that 0 and 1 are special for something. Is this true?

2

Yes, they're used for the serial interface, and are usually marked as such.