I've used lightbox2 in a D6 Project and it works fine.
In D7 however the template file is not recognized. What to do? I copied the tpl file into my theme folder (I'm using 'Basic'), flushed the cache and refreshed. The links are formatted like this: href="node/538/lightbox2" rel="lightframe". The lightbox opens, but only in standard layout, e.g. with all navigation and sidebars.