Multiple HD Failure?

Over the past 8 years or so i’ve purchased and run about 10 WD drives and never had an issue…until now.  I have a system w/ 4 drives, 2 WD Blacks (System and backup) and 2, 2TB Greens (media and backup).  For a few months now my system has been hanging on boot which i tracked down to the component checking, and it turned out that the two green drives were having issues.  Ends up that one drive, (2009 build) is totally gone, will not even format completely, and the other (2010 build) had a bunch of bad sectors.  

Any thoughts on what would cause two drives to go at the same time?  Both were running fine up until about a week ago. A friend thought i could have a faulty sata controller but drives behave the same in another computer.

There are many reasons why the drive might fail.

For information on how to get the best possible installation and how to handle  your drives please see the link bellow:

http://wdc.custhelp.com/app/answers/detail/a_id/981

Have you tried running a test on the drive?

You can use our Data Lifeguard Diagnostics software. Take a look at this article:

How to test a drive for problems using Data Lifeguard Diagnostics for Windows
http://wdc.custhelp.com/app/answers/detail/a_id/940

I’ve run the data lifeguard software on both drives.  The older drive will not even complete the check, newer drive limps through it but still have the errors.  I am in the process of copying all data to a new drive but keep getting cyclic redudancy errors on the read side.  I completely understand drives fail but find it very hard to believe that two drives woudl fail in a similar way at the same time, especially when other drives in the system are unaffected.