See https://drupal.org/node/2059887
The high used z-index of '9999' in jquery.stapel.js on line 546 can be problematic when an browser overlay is used that opens after initial page load.
In this case it is the admin overlay in Drupal, but it could be also a lightbox like solution to open images. Using a z-index of '99' solves the admin overlay issue for Drupal.
See https://drupal.org/node/2059887
The high used z-index of '9999' in jquery.stapel.js on line 546 can be problematic when an browser overlay is used that opens after initial page load.
In this case it is the admin overlay in Drupal, but it could be also a lightbox like solution to open images. Using a z-index of '99' solves the admin overlay issue for Drupal.