please take note of a small error on html semantics. Currently the plugin outputs this:
<div class="content" style=""data-thumb="URLOFIMAGE:>
Notice that there's no space between style="" and data-thumb which create error on validation.
What I did is change this code (/wp-orbit-slider/index.php line 389) from
$datathumb = 'data-thumb="' . $urlthumb . '"';
$datathumb = ' data-thumb="' . $urlthumb . '"';