WD Home Ed using eSATA disconnects with MacBook Pro

My 1 tb Home Edition for PC was reformatted to Mac. No WD drive manager used.  When I use the esata cable it disconnects unreliably and spontaneously.  It is OK with Firewire and USB.  eSATA cable works fine with G Technology drive from Apple Store.  

I am using MacBook Pro with a express card.