I'm not able to replicate this behavior here. Is it possible you had more than one Hero Lab instance running at the time? Is anyone else seeing this issue?
Nope, only the one instance. I loaded HL, and used the built-in updater to try to update to 8.6b. I ran into this issue when updating to 8.6a as well, and it was fixed the same way. Downloading the installer from the website, then running the installer instead. Both times I had only opened one instance of HL to check/perform updates.