Slimbox2 can cause problems as a Lightbox solution within the jQuery JavaScript framework in Joomla (in this case, Joomla 2.5). This can be caused by a conflict with the MooTools framework and other components that are loaded as part of the "<jdoc:include type='head' />" directive in the index.php file of the template set. So what can you do?
1) Disable MooTools and other JavaScripts – you can find a good guide for doing this, for example, here. In our case, the four scripts mootools-core.js, mootools-more.js, caption.js, and core.js were disabled.
2) If none of this helps, this article might be useful.
