Mountain Lion VirtualBox VM on Windows 8 Host: Can't Mount iPad

I'm trying to set up an environment for iOS development. My Mac OS X VM is working excellently, but I can't seem to mount my iPad.

The iPad does not show up under My Computer with iTunes installed. Unmounting the iPad from iTunes did not help. I tried uninstalling iTunes, after which the iPad did show up under My Computer, but I'm not sure if unmounting it somehow would help. I even have a filter set under the VirtualBox VM Settings.

Throughout all these steps, I get the same error when trying to mount the iPad on the guest:

Failed to Attach USB Device Apple iPad...

error:

Failed to attach the USB device Apple Inc. iPad [0210] to the virtual machine Mac OS.

USB device 'Apple Inc. iPad' with UUID {2f498ad0-976a-4173-b83a-a47df2b8278e} is busy with a previous request. Please try again later.

Result Code: E_INVALIDARG (0x80070057)
Component: HostUSBDevice
Interface: IHostUSBDevice {173b4b44-d268-4334-a00d-b6521c9a740a}
Callee: IConsole {db7ab4ca-2a3f-4183-9243-c1208da92392}

I can't seem to manage to mount it, which is the last step in my plot. Any ideas why this is happening?