Conflict with wp-media-manager-lite (don't know which is the faulty one)

[freeeflyer]

Hello All

If I activate the plugin wp-media-manager-lite the following message appears when I launch the editor..

Error thrown
Call to undefined function get_current_screen()

I've tried to add a require_once with the file containing said function, but it did not work..

If anyone can help. (I really need a media manager plugin, I've got hundreds of pictures to show)
Of if you know of one free plugin to add subfolders to the media manager..

Thanks