ZIP library will not excute a valid archive with some browsers !!

[eluser]alsemany[/eluser]
I used the zip encoded library , after downloading the file through the most three browsers
FF , Chrome , IE

Code:

$this->load->library('zip');
   $path = '/path/to/folder/';
   $this->zip->read_dir($path, TRUE);
   $this->zip->download('myfile.zip');

all the three zip files have the tree of the folder

but all of them except the file downloaded by FireFox have CRC32 = 0000000 for all files on the archive

the FireFox is the only browser give the CRC32 successfully
IE and Chrome give unreaded files on the archive with the check sum CRC32 = 0000000

Code:

using Windows 7