I believe there is a major issue with the new version of WPMU Dev plugin. When the plugin is activated, a user can not add media to a post/page properly. This issue is happening on ALL my installs. These are the steps to recreate the issue.
- Open a post/page to edit
- Click add media
- Upload image
- Choose insert image
Upon doing this, the media upload window closes as it should, but the image does not show up in the editor. If a user clicks preview, the reauth login page shows up, forcing a user to re-login.
Once the plugin is deactivated, image insertion works as it should.