You know, it is really strange that they say it is not Vista x64 compatible, when on WD Support > Downloads > My Book > My Book Essential Edition
it *clearly* states
This installer - WDDriveManager_x64.exe
or WDDriveManager_x86.exe (contained in the zip file) installs the Drive related light, button, and RAID Manager functionality program for Windows 2000, XP, and Vista.
I think you should contact them again and talk to someone in technical support - and perhaps read some reviews of this on the web, in particular to folks who already use this product with Vista x64.
Honestly, I can see the problem if it was not a driver but software, such as their DataLife tools or something else, that would be causing the problem, but it seems highly unlikely that they would be including a 64bit version of that tool if it were not 64bit compatible.
Mind you, I am not saying you're at fault in this at all - you're just the messenger, telling me what they said - and I am calling them out right now for what seems to be, superficially, as an utter lack of product knowledge.