Fairly new install of W7x64, updated to Dec 2016 .NET 4.6.2. Installed QTTB 1038, now I cannot create ANY windows ANYWHERE, not even in safe mode!
Thankfully, I had the Run Box in my Start menu, so I could open Regedit. I then manually searched for and removed all "QTTAB" related registry entries. After a restart, I could open a damaged-looking Explorer window, navigate to the QTTB installer, install it and then immediately uninstall it, then restart again, and I now have normal windows back again.
What went wrong?