Apparently the Comodo servers are being overwhelmed with everyone trying to update to the new version (they need to see how well CCleaner does this!). Several times I've got passed the 50% mark when an error occurs. So what happens to the first 50% of the files files? Thank You!

It depends on which software is used to download it.

Some software, when a download is interrupted the file is removed, and if you try to download it again, it starts again.

While download managers and most FTP clients, can start to download files, and the pause the download, or if the download gets interrupted, they can resume downloading the file from where it was.

In this case of Comodo, it depends on how the software is coded.