I often download Microsoft ISOs or very large EXEs from Microsoft's TechNet or iso.esd.microsoft.com

The other day when I downloaded Windows 8 Release Preview "http://windows.microsoft.com/en-US/windows-8/iso" I found incorrect checksums. So, I tested FDM v3.9 by downloading all of those ISOs and half of them failed SHA1 checksums. Especially if I Stopped and Resume them.

Does FDM v3.9 Rollback/Retransmit a few KB before the aborted/stopped download?

I then used JDownloader and Re-Download them and they ALL came back OK.

I then used uTorrent and created a torrent file for the GOOD file and used it to Re-check the bad file... to graphically show where the corruption is occurring... I found the beginning block and near the end or where it had to Resume because of timeouts was where corruption happens.

I also tried using a very old version of GetRigtht 5.2d & DownThemAll Plugin, and they BOTH were fine.

Tried FDM v3.9 on a different computer, an Intel Laptop and the same corruption happened.

Is this only happens on Microsoft Servers?

Can you please Verify this unusual occurrence?

Thanks!