This is driving me nuts.

I'm getting many reports of no "add to cart button" available on the product page.

If I test it myself the button is just there. I tested all browsers like IE, FF, Safari and Chrome.
It is also working on some friends computers. Also on iPad and other tablets.

This way I cannot replicate the problem.

I'm using ver 1.53. No new installed plugins, no new design or layout etc.

Please help, need to fix this asap
Thanks!

This is the website: http://www.dl-sounds.com