So, I've had this issue numerous times and I just had it again. However, the fix I posted on the official bug report here
https://community.openvpn.net/openvpn/ticket/592 worked again for me.
I stopped all virtualization software and kicked off the install again (didnt even have to reboot). The install went through just fine. The only virtualization software I use is VirtualBox and Sandboxie. I stopped Virtualbox machines and closed all Sandboxie Sandboxes.
It's most likely a driver conflict with another software. It's easily reproducible by just using the above software. I'm guessing it's mostly Sandboxie in my case. It may be something similar for everyone else. Check all of the services you have running in services.msc. Another way to try and help diagnose it would be using Process Monitor to monitor any errors that appear to come from the installer while you're installing.
BTW, this was with the latest version as of July 3, 2018: 2.4.6.