Hi Aravot,
I found the trouble JS file. RT uses the Gantry framework, and that framework has the mootools-1.2.5.js file. if I stop loading that extension, the add to cart and lightbox start working.. (by the way, the MT-Upgrade" does not affect VM, ON-OFF gave the same result.. but is I cut that individual JS file in Gantry , it solves it...
So what should be done? If this is a RT problem, can you clarify here, so that I can go to them and point to this post?
Thanks!