Hey frusciante299,

  I would suggest that you first install the latest MAC OSX drivers from the link below:

  MAC Drivers : 7.1.0

  http://line6.com/software/readeula.html?rid=4171

  Once the drivers are installed you will need to install the Line 6 Monkey application from the link below:

  MAC Line 6 Monkey 1.43:

  http://line6.com/getrelease?rid=4222

  Once Line 6 Monkey is installed, remove any additional unnecessary USB and firmware devices from your computer when troubleshooting this issue. Make sure to connect it directly to a USB port and not a USB hub, extension, or keyboard of any kind, preferably connect it to a USB port on the rear of computer. Try using additional USB cables and every USB port available until you are able to launch Line 6 Monkey and detect the device.

  Once Line 6 Monkey is launched apply any updates that are available until you have a green check next to each component.