Before you switch software, I would first check your Anti Virus program. Disable it and try again.
Does the error happen during download, or when you try to install?
Based on my personal experience I would run screaming from AT&T, but that has a few decades of blind hatred of that company.
Do you get this when you attempt to download the installer (either from ProSeries Ty19 or a link from somewhere)? Or when you run the installer? If it's when you run the installer, at what point? Right away or after you select a bunch of install options?