Possible regression between uno and uno R2

Development Tools IDE 1.x
1

Hello.
We have been getting problems recently with arduino boards.

We use I-wire on pin7 for some ibutton reading and had the arduino R2 halting immediately on powerup. Pressing the reset button makes it boot correctly.
We finally found that simply taking a 4.7k resistor from the board 5V to pin 7 causes the problem. On original UNO, this works.

Can you reproduce? (we can, each time, using any program, even 'blink')

Has anyone got any idea on what causes this behavior and how to solve it?

Thanks a lot.

2

Can please anyone try to put a 4.7K resistor between the uno 5V and pin7 on a R2 board and tell me if the board boots or not?

I've been testing 8 boards on the 40 i have here and all show the problem. I'm wondering if it's a design problem or just the serie.