[SOLVED ]upload problem: ttyACM0 not found

Development Tools IDE 1.x
1

When upload, it prompt "serial port /dev/ttyACM0 not found, Retry the upload with another serial port". And the first choice available is /dev/ttyACM0. I selected it and upload fail.

But ls /dev show the ttyACM0 exists, why?

My environment:
UNO board
software 0022 (run as root), RXTX-2.1-7
Ubuntu 10.04

UPDATE:
solution: arduino 8u2 DFU

2

Try unplugging your arduino, closing the Arduino IDE, plugging your arduino again and open the Arduino IDE again. Sometimes if you unplug your Arduino and plug it again, the IDE won't recognize it.

3

After update 8u2 firmware, the problem disappear.