[Plugin: NextGEN Gallery] Error on live server

hello
i have installed Nextgen gallery and everything is working fine on my test server(wamp) but when I have uploaded on live server thought the gallery and images which is already added on test server are working fine but when i am trying to add gallery or image on live server it is giving me error on pop up.for eg when i am trying to add an image on post thought the pop up open up but it is giving me error as

Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.

thank you in advance

http://ww.wp.xz.cn/extend/plugins/nextgen-gallery/