Ftp user can't unzip files with « upload and download » app

hi all,

I’ve got a problem with my ftp users wich can’t unzip the zip files.

The upload of the zip files works, but at the end when it unzip i’ve got this error :

/home/etudiants/public_html/XXX/YYYYY.zip (8615 bytes) Failed : standard in must be a tty

For information, my ssh account works perfectly, it appends only for my ftp account.