Do you have many files/images in your media folder? When you hit the "files" button it takes a long time to load as it loads all the files/images in the folder. What if you have a few hundreds of files...

This plugin provides a button for quick and easy files upload.

By default it uploads files in blog's media folder (if you create or edit post in Blog B all files get uploaded to /media/blogs/b or whatever is set as default media dir for this blog ).

You can also enable a directories select tree in plugin settings and choose a directory before uploading files.