marcfitt on "[Plugin: WooCommerce - excelling eCommerce] downloadable/digital problem"

I have a couple of digital products that worked fine until yesterday. I have tried to add a new one and it's seem that my whole digital product are broken. We can download the file after we order one, but the file cannot be open... For example, a zip file will always stay a zip file when we unzipp it after we dowload it, an excel&pdf file can't be open because the file is broken.
Plus I can't upload directly a file in woocommerce because the file don't go in the upload/woocommerce, he goes in the normal wordpress upload directory so it will not be secure.
So that's why I upload it directly in via http://ftp... but everything don't work.
Please help

http://wordpress.org/extend/plugins/woocommerce/