Man, I'm sorry to hear that. Sounds like that's at least two people who have had a bad upgrade of the base IDE. I installed (vs. upgraded) 2019.1 RC when it was released a week or so back, and then today I upgraded that to 2019.1 GA. I haven't had any issues, but I also didn't try an in-place upgrade.
In general I would recommend parallel installs for major new builds. Some of these small patches, e.g., 2018.3.6 from 2018.3.5, are generally fine, but when you're talking about a major seasonal release, downloading the full installer and just installing it beside the current installed version seems like the safest bet to me.
Regards,
Scott