Had a struggle getting this jquery lightbox working recently, the solution for me was to alter the markup of the popup div because some divs were not closing correctly with />.
Basically I had to replace this portion of code:
/**
* Create the jQuery lightBox plugin interface
*
* The HTML markup will be like that:
<div id="jquery-overlay"></div>
<div id="jquery-lightbox">
<div id="lightbox-container-image-box">
<div id="lightbox-container-image">
<img src="../fotos/XX.jpg" id="lightbox-image">
<div id="lightbox-nav">
<a href="#" id="lightbox-nav-btnPrev"></a>
<a href="#" id="lightbox-nav-btnNext"></a>
</div>
<div id="lightbox-loading">
<a href="#" id="lightbox-loading-link">
<img src="../images/lightbox-ico-loading.gif">
</a>
</div>
</div>
</div>
<div id="lightbox-container-image-data-box">
<div id="lightbox-container-image-data">
<div id="lightbox-image-details">
<span id="lightbox-image-details-caption"></span>
<span id="lightbox-image-details-currentNumber"></span>
</div>
<div id="lightbox-secNav">
<a href="#" id="lightbox-secNav-btnClose">
<img src="../images/lightbox-btn-close.gif">
</a>
</div>
</div>
</div>
</div>
*
*/
function _set_interface() {
// Apply the HTML markup into body tag
//$('body').append('<div id="jquery-overlay"></div><div id="jquery-lightbox"><div id="lightbox-container-image-box"><div id="lightbox-container-image"><img id="lightbox-image" /><div style="" id="lightbox-nav"><a href="#" id="lightbox-nav-btnPrev"></a><a href="#" id="lightbox-nav-btnNext"></a></div><div id="lightbox-loading"><a href="#" id="lightbox-loading-link"><img src="' + settings.imageLoading + '"></a></div></div></div><div id="lightbox-container-image-data-box"><div id="lightbox-container-image-data"><div id="lightbox-image-details"><span id="lightbox-image-details-caption"></span><span id="lightbox-image-details-currentNumber"></span></div><div id="lightbox-secNav"><a href="#" id="lightbox-secNav-btnClose"><img src="' + settings.imageBtnClose + '" /></a></div></div></div></div>');
$('body').append('<div id="jquery-overlay"></div><div id="jquery-lightbox"><div id="lightbox-container-image-box"><div id="lightbox-container-image"><img id="lightbox-image" /><div style="" id="lightbox-nav"><a href="#" id="lightbox-nav-btnPrev"></a><a href="#" id="lightbox-nav-btnNext"></a></div><div id="lightbox-loading"><a href="#" id="lightbox-loading-link"><img src="' + settings.imageLoading + '" /></a></div></div></div><div id="lightbox-container-image-data-box"><div id="lightbox-container-image-data"><div id="lightbox-image-details"><span id="lightbox-image-details-caption"></span><span id="lightbox-image-details-currentNumber"></span></div><div id="lightbox-secNav"><a href="#" id="lightbox-secNav-btnClose"><img src="' + settings.imageBtnClose + '" /></a></div></div></div></div>');