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When the lightbox is in a hidden tab panel, on page load the lightbox has no size dimension due to the {display:none;} panel and cannot be initiated properly. That is why the lightbox is not working properly. If the lightbox has a functionality that will re-initiate itself when finding it begin to have a dimension, that will solve the issue. Otherwise, you cannot use the lightbox within a hidden panel.
The advanced version, jQuery Tabs, has an event handler: onTabSelected. Maybe you can use the event handler to reload the lightbox. For example, some of our Ninja Slider users are including this call, nslider.init(), to initiate the Ninja Slider if it is inside the jQuery Tabs.