Download Zip File

When a cutomer made a purchase and downloaded a zip file, the file said is corrupted. After breaking my head of what it should be, i tried modificating the sendFile function, after some test i commented the "header('Content-Length: '.($seek_end - $seek_start + 1));" Line, the problem stop. I have the 1.6.0 version, is this a bug from you or what is wrong?

Other users don't have the issue and we didn't change anything on that end for 1.6.0.
That line allow to handle download accelerators and resume capabilities. So you can sure do without it.
Are you using a specific tool for the download ?