I’ve had the exact same problem on my WD Portable Ultra 2TB HDD. The problem only started happening once I upgraded the firmware. So I sold it and now got a WD My Book 3TB but I have learned my lesson, I will not be upgrading the firmware. the firmware that my previous WD My Passport Ultra had was v1.025 if that matters.
WD does not offer its customers to downgrade the firmware so you are out of luck.
And to the staff member that suggested to update the USB Drivers! PLEASE for the love of God! what kind of technical support is this? Windows 8 does not need and does not have USB 3.0 Drivers. They are now built into the OS and there is no way of updating them!
