It might only affect you if you have drives shipped before June. All drives since that date are AOK.
This irritating phenomenon happens because of a feature that cuts idle acoustic noise in desktops in an IDE RAID environment.
But WD says there's an easy answer - you can just switch this feature off and Bob will be your uncle.
So if you've been wondering what's happened to your EIDE drives, worry no more and head over here for more info.