juergenP, i renamed my vst3 folder and tried again,m this time it launched. its probably some old crappy vst i had in there. all good now. thanks so much for you time.
Just a tip: Instead of renaming your vst3 folder, you can always start Cubase in safe mode with third party plugins disabled. The safe mode windows comes up after a crash automatically, or you can force it by starting Cubase and immediately hitting the keys Ctrl-Shift-Alt (Windows) or Cmd-Shift-Opt (Mac).