This extension uses a xClass on tslib_cObj:cImage . So there are conflicts with other extensions that XCLASS this function as well. The following lightbox-extensions are therefore not compatible:

kj_imagelightbox, kj_imagelightbox2

Use instead a lightbox that does not xClass the core of Typo3:

perfectlightbox, pmkslimbox

If anybody has a idea how to avoid the xClass pleas let us know. - maybe using a stdWrap that calls a user function could be a way? Any recommendations?