Products did not show on products page - NEED HELP FAST

[q-skins.dk]

Hi all.

 

I have a prestashop which have been running for about 6 month, but earlier today i tried to install a new theme which went wrong. I took a ftp. backup before the install which i have uploaded again. But now all my categories and the products in the categories is working fine, but when i am clicking at one of my products it go to the products html site, but now the products site is not showing the site is compleately blank? what to do?

 

Please help.

 

 

Here you can see what i mean, the site is just blank.

 

http://q-skins.dk/iphone4-cover/19-iphone4-himmelbla.html