I just wonder why some people use Dropbox testing versions? Testing versions of Dropbox are often buggy. They are released for testing purposes. So using test versions of Dropbox you just asking for trouble. If your Dropbox/Boxifier syncing is important for you, stay with stable Dropbox versions.
Just to add to what @neko said, we recommend using the stable versions of Dropbox and unchecking the Include me on early releases in Dropbox account settings: