I have tried every single thing* possible to test this problem.
Basically I am selling a digital download in zip format, I have tried creating the zip in windows and mac with every program possible and downloading on both platforms after payment with a secure link.
The files are not corrupted on upload as I can download them from the ftp in perfect working condition.
But there is a problem with ASCII coding which causes the zip or any other compress archive... to be corrupt when I download onto my mac.
I am using Chrome, but will test in other browsers and let you know if there is any change.
Windows handles the files perfectly...
Is it the nature of ASCII in wordpress? Help me :)