I’ve got the newest version of the Lightbox Plus plugin (1.5.3.1). Everything seemed to run fine, until I checked my IE page loading time. While Firefox and Chrome take 1 or 2 seconds to load a page, IE takes 10. After some testing I discovered it was the Lightbox Plus plugin that was causing the delay.
I hope you’ll come up with a fix, since this is the fastest (and most beautiful) lightbox plugin out there.
Maybe IE isn’t able to handle the jQuery?
