I am trying mattlgroff's util and it is hanging at writing modem. I haven't been able to get out of the fastboot mode due to failed flashes.
Something on your machine is interfering with flashing. That's about all I can tell you. You're going to have to do some work to figure out what's going on here. Basically it's just locking up sending the files to be flashed. That goes back to what I said about port, cable, or driver. I know you said you've done it before, but, clearly something has changed.