Wysiwyg, ckeditor disappers when click "Add another item" button
I had this problem as well. This was fixed in http://drupal.org/node/1155678#comment-5358290 by adding a detach function to the WYSIWYG behaviors. You can apply the patch at the above link (that's what I did) or you should be able to download the 7.x-2.x-dev version (I haven't tested that) since it's been committed already.