After upgrading from beta7 to beta8 integration with Colorbox stopped working. Only reason I found - colorbox-display.js is attached but not finally not loaded. Why? I don't know. But if load it using drupal_add_js() and drupal_add_library() functions it works ok.
So I've attached patch. And maybe somebody can explain why attached js was not loaded.

Files: 
CommentFileSizeAuthor
media_gallery_colorbox.patch1002 bytesGeorgique