Image Upload issue – Thumbnail not generating

I am using the following
Wordpress 3.9.2
Nextgen Gallery 2.0.66.16
NextGEN Public Uploader 1.8.2
When I am trying to upload the images using public uploader some of the images are not uploading. Please refer the following
Upload url: http://www.zerosofttech.com/dev/wordpressnominal/creative-images/
one of the image which is not uploading http://www.zerosofttech.com/dev/wordpressnominal/wp-content/gallery/creative-images/leaf-boat.jpg

Please help me to get out of this problem. It’s very urgent

https://ww.wp.xz.cn/plugins/nextgen-public-uploader/