donamh :
Unfortunately it's not the cable as I've switched out cables and have the same issues. I've tried with other computers as well, and the same issue arises.
This is very unfortunate and unpleasant.
🙁
Here's something that you can try to resolve the issue:
1) Go to Control Panel
2) Change view by to Small icons (View by is in the top right corner)
3) Go to Power Options
4) Then Click "Change plan settings" for the power plan you are using (text is in blue)
5) Then Click "Change advanced power settings" (text is in blue)
6) Then another window will pop-up. Scroll down and look for "USB settings"
7) If you click the little plus on left of USB settings, "USB selective suspend setting" will appear
8) Press the little plus next to "USB selective suspend setting" as well and "On battery:" and "Plugged in:" will appear
9) It should say DISABLED so switch it to DISABLED for both "On battery" and "Plugged in"
10) Then press Apply and then OK (Unless you want to configure other plans as well.
If this doesn't help you should inform our tech support about this problem.
I'd suggest to give them a call and RMA the WD My Passport. If it's still under warranty you should be able to get a replacement.
Contacts:
http://products.wdc.com/support/kb.ashx?id=rwH2ww
How to RMA:
http://products.wdc.com/support/kb.ashx?id=A4ZaVB
Good luck!

SuperSoph_WD