This is a rather old thread, but I hope it is still alive. I have the same problem when downloading any code to the OpenCM 9.04c board. I am using Ubuntu 14.04 32b. The device is correctly identified when I plug it in:
[65736.448298] cdc_acm 5-1:1.0: ttyACM1: USB ACM device
[65812.932306] usb 5-1: USB disconnect, device number 15
[65818.224104] usb 5-1: new full-speed USB device number 16 using uhci_hcd
[65818.390157] usb 5-1: New USB device found, idVendor=fff1, idProduct=ff48
[65818.390167] usb 5-1: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[65818.390175] usb 5-1: Product: ROBOTIS Virtual COM Port
[65818.390181] usb 5-1: Manufacturer: CM-900
[65818.393281] cdc_acm 5-1:1.0: This device cannot do calls on its own. It is not a modem.
[65818.393333] cdc_acm 5-1:1.0: ttyACM0: USB ACM device
I added my user to the dialout group so that I don't need to change permissions (I tried changing permissions anyways).
Pressing the board button while connecting does not help.
The only way to do something is to boot my PC on Windows 7, press the board button when connecting, restore the firmware of the board using RPlus (it also takes some attempts until it recognizes the board and I can reset the initial configuration) and then download code to it (also requires several attempts). However, I would really like to download code from Linux/Ubuntu.
Any hint what could cause the problem? Maybe the configuration of the serial communication? The library?