Have you tried installing right after a reboot?Yes, I tried. It makes no difference.
The installation process cannot read that tmpA3.tmp file because some other process is locking it. Temp files, or folders in general, are save to delete as well. So you might wanna give that a go.This file (and it has random name every time - "tmpA3.tmp", "tmp923.tmp", "tmp92B.tmp", "tmp93A.tmp" etc) auto-deletes itself when I close the critical error message, so there's nothing I can do about it.
NET Framework downgrading fixed the issue, I'm back in the game :P