Symptoms

There are four symptoms:

1. Clicking on thumbnail opens a new window together with the lightbox dialog.
2. Comments overlap with each other in Internet Explorer 7, as reported in Clicking on a Thumbnail Opens a New Window and a Lightbox.
3. There may be warnings about mixed secure and insecure content in IE.
4. Drop-down menus are not displayed on some pages where thumbnails are used

Cause

This problem is caused by Advanced Macros 1.6.4.

Resolution

Uninstall the Advanced Macros (1.6.4) from Administration >> Plugins, then restart Confluence. Confluence will load the bundled version of this plugin.