I’m afraid I cannot help - however I have a similar problem. I have just upgraded the fimrware and after a PC restart (running XP) my WD extarnal drive is no longer recognised anywhere on the PC. I have also tried to connect to a laptop running Win 7 and it does not recognise the drive.
If the original software that came with the drive worked, perhaps you could disconnect the drive, uninstall the updated software and then reconnect the drive again. This should allow the older version WD software to re-install itself just as it did when you first connected it. If you are doubtful of this idea, you can set a system restore point before trying it.
The drive will probably go through the complete back-up process all over again.