media stoped working

i installed this plugin in my wordpress 3.5.1
and media stoped working when i try to upload a picture in my media when making a new post. it show an error. An error occurred in the upload. Please try again later.
i deleted this plugin but problum is still there.

and on another domain i have wordpress 3.5.1. i install this plugin. and media stoped working when making new post. but when i deleted this plugin problum was solved and media works fine. but on my other wordpress after deleted this plugin problum is still there. can you tell me how can i make my media work again. thanks

http://wordpress.org/extend/plugins/custom-ads-sidebar/