I’m Posting this just incase it’s useful information for someone else.
So a few days back I completely broke Cubase 11 and 12, which had both been working perfectly until that point. (One crashed on startup everytime and the other left me unable to load any projects at all without crashing.) I was sweating at no longer being able to access any of my projects and was starting to panic until I remembered that earlier I had done what I thought was some housekeeping on my pc. I had noticed that there were some VST2 dll’s in the :Program files/Commonfiles/VST3 Folder, So I deleted them, Seeing that there were already VST3 versions of the same plugsins also in that folder, I assumed it would be safe and perhaps even benificial. Big mistake, this completly threw Cubase to my surprise. And lead to aforementioned crashes every time I either tried to load the program in one version of cubase or load a project in the other. (Can’t remember which version did which, Sorry - And bit scared to try reproduce again)
Luckily having realised my potential mistake I was able to restore the deleted files from the recycle bin and everything then worked perfectly again - Phew! I had in the mean time tried trashing prefs etc, but that did not resole problems.
Pics just to show folders I messed with, and as I said all I did was remove what I thought should not be there anyway. Perhaps this might help someone else, Or at least serve as a warning to be very careful what you delete - Maybe stating the obvious there I know!