It’s strange that it should work on one PC and not the other. I have noticed that, on a few PCs, windows can take a couple of minutes to assign the driver. Often the Crumble gets unplugged before it’s finished and the process starts again. From your description, it doesn’t quite sound like this is the problem, however, I think it’s worth trying to leave the Crumble plugged in for a few minutes to see if anything changes.
This could also happen if another program is accessing the USB device. This could be another instance of the Crumble software. If you haven’t restarted the desktop, it might be worth doing.