Hi,
What you found is indeed the solution, and it's still what I would recommend.
The fact that it doesn't open the popup when you click on the image means that mootools (the system which generates the popup) could be initialized on the page.
It could come from a conflict with jQuery (another javascript library), and in that case, you can use the plugin jQuery Easy to fix that, or it could be another javascript error on the page (you can check the error log of your browser for that).
Or it could also be your template or another extension forcing the removing of mootools on the page (you can check the HTML header of the page for the presence of mootools)