The most likely cause of this problem is a bad USB cable. Try using a different USB cable first. Also, if you are plugging the QuNeo into an unpowered USB hub, try plugging directly in to the computer or use a powered hub.

On certain rare occasions one might experience this problem:

2011 MacBook Pro USB Port Problems

USB ports on Apple laptops are connected to an internal USB hub that also feeds the keyboard, trackpad, iSight camera, Bluetooth, and IR receiver. Some 2011 MacBook Pro models (and potentially others) shipped with an internal USB hub that exhibits connectivity issues when a device that draws a lot of power is plugged in. This results in the port completely shutting down, and you will not be able to use any USB device in that port until it is reset.

The internal USB hub in question is Vendor ID: SMSC, Product ID: 0x2513. To find out if you have this hub installed in your computer, go to the apple menu at the top-left of the screen and select "About This Mac". In the window that appears, click the "More Info..." button — this will open System Profiler (alternatively you can open System Profiler directly from Applications --> Utilities --> System Profiler). In the "Contents" column on the left, under "Hardware", click on "USB". Click on one of the "USB High-Speed Bus" options in the "USB Device Tree" area and some information will show up in the field below. Under the "Hub:" section, check to see what the Product ID and Vendor ID are. The hub we have noticed problems with is Product ID: 0x2513 from Vendor ID 0x0424 (SMSC).

If your USB port is no longer working, there is a fix. You should first try completely shutting down your computer and starting it back up again (simply restarting may not work). If it is still exhibiting the same problem, then you will need to reset your SMC (System Management Controller).

To reset the SMC:

1. Shut down the computer

2. Plug in the MagSafe power adapter to a power source, connecting it to the Mac if it is not already connected

3. On the built-in keyboard, press the (left side's) Shift-Control-Option keys and the power button at the same time

4. Release all the keys and the power button at the same time

5. Press the power button to turn on the computer

Your SMC should now be reset and your USB port should be working again.