I am yet another person who has this exact problem. My passport came with version 1.6. Since upgrading to version 2.3 my backup has not worked - been a few months now. Previously I reinstalled the original SW and all was good until Windows Update automatically updated the SW again. Doh!
I no longer have the disc that came with the device so I cant “downgrade” again
Today I upgraded the SW to latest V2.4039 - and guess what… it still doesnt work!!
WD are simply not aknowledging the problem even exists, even though there are 100s of complaints referring to this on the web.
Sadly time to move away from WD me thinks 
If anyone can help?!
