Sorry the last post was incomplete: problem is that the serial changes (from the cotrrect choosen port com3 to com1) as soon as I connect some actor/sensor to the arduino. This occured first time when I unplugged the arduino while running! before everything was fine.

perhaps in the intern software of Arduino something was shot down?

If anybody has experience with this I would be glad to hear about.

Thanks!

I have the same problem on my windows and no idea how to fix this.