I'm sorry but, your log shows the Couatl_updater2.exe cannot be found, which can only indicate some kind of external interference from another software, most likely the antivirus because, if you can see the file, the only possible reason for the error is the antivirus blocking from executing the updater so, it looks AS IF it was removed, even if it's not.
- Configure the antivirus to exclude the Addon Manager folder from scanning
- Run the Updater again
Be sure you don't have ANOTHER software which is doing the same thing, like a defective anti-spyware or similar.