Unrecognized Arduino Uno R3 in DFU mode on my Mac OS X Mavericks 10.9.4

I am trying to flash my Arduino Uno R3, but my Mac doesn't appear to recognize it is connected.

When it is not in DFU mode, it recognizes as a 'Communication device', on the system report, and I can upload code and run it perfectly. If I try to put it on DFU mode, the device disappear when I put the jumper, and when I take it off the same device comes back

I have a similar problem as the following link: http://forum.arduino.cc/index.php/topic,134078.0.html

I have already installed usblib and dfu-programmer 0.5.2

When I try the following command, I get the results:

bsessoMac:HexFiles user$ ./dfu-programmer atmega16u2 flash UnoJoy.hex 
dfu-programmer: no device present.

What can I do for my mac recognize it?!? =(