My Book Home not detected by iMac

Well, I seem to be experiencing multiple WD drive failure as one drive after another in the last two days has decided that while it might be seen by my Macbook Pro, it will not be mounted.  As I tried the different cables, different ports, different power cables, plugging in and out in prescribed order, I’m at a really confused point.  For the moment, my computer still recognizes my passport.

Is anyone else solving these problems?  Has there been a recent upgrade for both WD and MAC that’s conflicting?