Some of our themes might not support Drupal overlay module. This is because these themes comes with latest stable version of jQuery.
If you check the error using inspect element of browser, you will find following error message.
TypeError: jQuery.browser is undefined
The overlay module do not work with jQuery version 1.9 and later. It's because $.browser is deprecated in jQuery 1.9 and overlay module need this to work. So, its good to disable overlay module from: