I've got quite a problem over here, too .. I use smf 1.1.16 .
It doesn't work .. when i click on an image that simply open a new blank windows with the right dimension image..
For istance :
i have this into a post:
if i click that, the browser transfer me in a new blank page at the address :
doesn't act like a lightbox ... it seems just change the simple image in a "clickable" one.
May i do something ?