When I try to upload Blink to my Duemilanova, I get the Serial Port 'Com4' error. It suggests that I quit any programs using 'com4'.
I am sure that I don't have another program using 'com4'.
This is version 18 of the Arduino IDE. I am running Win2K with Service Pack 4. I have tried reloading the USB drivers without any change. I have also tried the reset button tricks that have been suggested, but that has not worked either.
The L led blinks with an uneven pattern, which I think is the test code that was left on the Duemilanova.
Thanks for your assistance. JHoward