I have several Western Digital drives and generally they work well. I do currently have one has started to fail, I get errors saying it was disconnected every time I wake the computer from sleep. That's just to provide some perspective - I'm not aware of a systemic problem with these drives, although I'm sure Google will help you unearth any similar problems.
I'd recommend you use Disk Utility to check the drive first of all, and run a "Repair Disk" on it. If Disk Utility can't even see it, sometimes the cable might be the problem. Can you try a different cable? Do you have access to a different computer to connect it to so you can check the drive there?
When you say "the system no longer recognises it" perhaps you could provide more information. Do you mean you receive an error message of some sort, or do you mean it simply never shows up? Of course, I need to ask - does the drive spin up, show a power light, etc.? You might assume that we'll assume you've done all the basic troubleshooting, but it would probably be better to explain what trouble shooting you've done and precisely what is happening.
If you have an Apple store near you, it may be worth taking your kit there and seeing if they can help you. I think you can book in to receive assistance.
Hope some of those suggestions help you fix the problem.
Ivan