you can check here http://audiojungle.net/category/music/electronica/dance
I have the same problem. For now helped thumbnail remove and keep the default.
Thats not my item
Seems like the url path of the tumbnail is not pointing to the right place. The author can maybe try editing the tumbnail, but I am not sure if this will work. I think Envato will highly appreciate it if you let them know about this
( http://support.envato.com ) so they can prevent this from happening in the future.