This document instructs a workaround for a very common issue with using USB devices on a Parallels Windows virtual machine on Mac. 
If you have ever plugged in a USB device to use with a Windows virtual machine, you may have received the following error message:
 
“USB device you are trying to connect to the virtual machine is being used be another process. 
Wait 5-10 seconds, then try to connect the device again. 
If this does not help, find the application that blocked up the device and disconnect it manually.”

This error appeared when connecting a BlackBerry 8700 device to the virtual machine.
After waiting 10 seconds and reconnecting the device, the same error appeared (no surprise).
Up to this point, Parallels has not released an official solution to this problem.
The following procedure is a temporary workaround, and may need to be repeated after restarting the virtual machine or host computer, or if new USB devices are introduced

1. Leave the virtual machine running, and minimize it to the OSX system tray.
2. Launch Terminal.  (Go > Utilities > Terminal)
3. Type in this command: kextstat

A list of device drivers in use will appear.  Expand the screen to see their full names.

Notice the last three drivers are related to the BlackBerry device. These drivers are currently running on the OSX side.
Because of this, when you attempt to use the device on the Windows side, it causes conflict.
In most cases it will be the last three or four drivers that are in the list that you will have to manually kill.

4. From here, type in the following command: sudo kextunload –b device.driver.name
Where device.driver.name is the full name of the driver in use
(in this case, the first one of three is “net.pocketmac.driver.Blackberry USBDev”)
5. Next, unload the other drivers using the same command, but with the appropriate device.driver.name

You should receive the “unload successful” message from Terminal after each command.
(You may have to provide the user password for the first unload command)

6. Now, return to the Parallels virtual machine and plug in your device.  The Windows virtual machine should see the device, and it should function properly.

 

If you continue to experience problems, please see the Parallels website.