(Per this Forum Sticky): Each USB port is capable of delivering 500mA @ 5Volts max and
each port has built in semiconductor fuse that disconnects when external device power drain exceeds rated power output.
This fuse will heal itself once the offending device disconnects. etc etc
This is true maybe twice a week for my (APR 2013) 1TB My Passport - BUT -
my newer (JAN 2015) 1 TB Ultra has Never “Disappeared” because of this USB Port Fuse reality.
[One Drive’s “Continuous Backup” is always DISabled - Only one running at a time.]
Removing & Re-Inserting the USB connector is all it takes to [make my Files RE-appear] but it gets old.
IS there a newer Design Improvement in the Ultra that has prevented this or have I just been lucky so far?