Products and modules translation problem

[tittimoto]

Hi, I'm an italian user and I use Prestashop 1.5.6.0

I want to translate in english a site based on Prestashop 1.5.6.0 but when English language is on I can choose the language from the Front End, but I can not modify the products and modules from the back end.

I imported the en.gzip package and I think that the configuration is ok.

From the backend it's impossible to switch the language to translate products and modules because the english flag doesn't appear.

Thanks
Tiziano