My solution:
1) I copied the whole VST Plugins folder to a new place (i've called it VST Temp).
2) Rescan Plugins (with nothing in it, so it created a new config file, with no plug ins)
3) Started moving from VST Temp folder to the VST Plugins folder, the more troublesome first (Arturia, Ozone 8)
4) Rescan again.
5) Check what it found.
6) Repeat process....
7) and so one. I've moved no more than 4 folders at a time, and re scanning.
It took me like an hour, but i manage to get Ableton to recognize every plugin.
With the other methods, i was missing like 30 plugins.
Anyway, hope this helps someone.