I tried to use Lightbox2:
A very strange situation indeed.
With the help of one of the forum members, DesignCity (thanks again), the solution was found: just place ContentNegotiator::disable() in the config file. It seems that the ContentNegotiator tries to do strange things with Safari...
Perhaps other people ran into this as well, so this might help you a little bit more in the right direction. If you have any questions, let me know.
(Edited for spelling)