thickbox not opening in seperate pop up window.

[kayotics]

I'm currently running 2 shops with prestashop and i've got a weird issue that i can't resolve.
When you click the product in one of my shops the larger thick box image pops up in a new window where you can hit escape or click close to close it.
In my other shop the photo loads on the same page as the shop but puts the product on the bottom left side of the page and cuts out half the image. I'd obviously much rather have the box pop up but i can't figure out how to make it happen.

Has anyone had any issues with this?

Any help would be greatly appreaciated.

Thanks,