Hello!
I think I can add the USB problem to the long list of known issues of the Marantz PMD-661 MKIII:
Audio files are transfered too slowly (0 - 1.500 kb/s instead of 30.000+ kb/s, USB 2.0) to my laptop if I connect the unit with usb cable. The device description is "Marantz PMD561" and not "Marantz PMD661" (USBDeview).
If you have any experience with this problem please send a message.
It's a new unit. I am using a laptop with Windows 10 (all USB devices work well except the PMD-661).