When I first installed the Arduino software on my Mac OSX 10.8.5, I followed the instructions in the Arduino Projects Book. But when I selected the serial port /dev/tty.usbmodem1a1221 according to instructions, it wouldn't upload anything. So I tried one of the Bluetooth ones (Sorry, I don't remember which) and it worked. Later, it stopped working, so I tried to go back to usbmodem, and it was gone. What should I do to get it to upload?
Thanks so much!