Image Zoom Giving Problem

I am facing one problem regarding image zoom addon.Whenever i hover mouse on main image for a product instead of zooming it , it gives a small image of it.For rest additional image it works properly.I am facing this problem for main image for many products.Please see the attached screnshots.

Any help will be appreciated.

Thank You.

Screenshot from 2015-03-27 15:03:07.png

Screenshot from 2015-03-27 15:03:21.png