If your site contains thousands of files, media library try to load All of them, but not Uploaded to this post first. This cause hanging of interface.
After long excavations of library i've find the way to change the default-view of the Media-Library from "All media items" to "Uploaded to this post". But i had to edit core library file media-view.min.js.
You can download the solution for wordpress 3.5 and 3.5.1 on this page. Don't forget to backup old file.
If there are another ways to do it, please tell me how -).