Was playing Exile mod and I exited the game normally but got a memory access violation error similar to the DayZ exit message (I have both games). Thought nothing of it - close down go to sleep.

Today Arma 3 won't launch - with no mods added so vanilla Arma 3. I get the launcher which launches the main window but I never get off the splash screen with Arma III on it.

I suspect my previous nights exiting error issue has left something in an inconsistent state.
Verified integrity of game cache with no issue - all OK.
Just will not even load Arma 3 now as a vanilla game.