we’ve seen reports of issues with Windows, and are currently troubleshooting the USB device drivers on the firmware side. It works fine most of the time, but in some situations it seems that Windows decides to use the wrong driver.
The workaround at the moment is to remove the driver for the device, and then manually load a class-compliant MIDI driver.
I’m not a Windows expert by any description so I won’t try to explain how to uninstall whatever driver Windows decided was right, but post back here if you have problems. We’ll try to rustle up proper instructions asap.