Got today the same problem, with a bunch of strange symptoms - opera won't open at click to icon (at the same time, a bunch of dead processes accumulate in the list of running programs ), sometimes it launchs finally (UI is opens), but no speed dial shortcuts, and no browsing history (though bookmarks section still comtain\show all bookmarks properly).
How a much years i use opera, such madhouse first time.
Latest version \ Win10
Tried "cleaning browsing data" - not helps. Moreover the icon of cleaning continued spinning endlessly after cleaning process, so, forced to close browser without cleaning end alert.