Preview image of thumbnail is not displaying

Hi,
I can add an album to specific gallery. But the preview image of the album is not displaying. But when I clicked on that album it shows all the images in the album.

Only preview image is not working. It’s not getting appropriate image path. My question is why?

Please help out here.

Referred images links are given bellow:
http://s7.postimg.org/967gutw6z/image.png
http://s7.postimg.org/wumyq3sqj/image.png

Thanks,
Naqib

http://wordpress.org/plugins/nextgen-gallery/