Cannot upload programs thru one usb port but can through the other usb port

Development Tools IDE 1.x
1

Mac OS 10.7.4
Arduino 1.0.1
Processing 1.5.1
Nano
Have successfully uploaded programs in the past.
status: newbie

I am able to upload sketches via one usb port but not the other. I was able to use both previously. I have confirmed that I'm switching to the proper serial ports when attempting to upload.

Here's what I was doing before the trouble:
I successfully followed this tutorial (pressure sensor + arduino + processing signal analysis |) and got it work. I used this code in Arduino:

// The Arduino code.

#define ANALOG_IN 0

void setup() {
Serial.begin(9600);
}

void loop() {
int val = analogRead(ANALOG_IN);
Serial.write( 0xff);
Serial.write( (val >> 8) & 0xff);
Serial.write( val & 0xff);
}

After quitting Arduino and Processing and restarting, the serial port I was using is no longer allowing me to upload sketches. The other usb port is working but I'm afraid I'm going to screw that one up too. Any ideas on how to reset only that one disfunctional usb port and prevent the issue?

2

Check if the mac thinks there is something connected to the port. Will the port use when you plug other things in it?
what were you measuring with that sketch? Any chance you shorted a high voltage to the arduino's 5V pin?

3

The solution appears to be that oldest of all solutions: I simply restarted my system.

Everything is working properly now. Thanks for advice and being such an awesome, supportive community.

4

That sounds like the mac decided to shut down the port because of over current. Looks like you shorted something out.