I used a similar device, Novatel u727, for quite a while and saw a problem like this from time to time. It happened when the usb device was not present, so it couldn't eject the device. I would remove the usb modem and re-insert it to get the devices created, then I could eject it. It would take a minute or two, so don't try to eject it right a way. Hope this works for you.