You can goto the URL opera://about, take note of the "profile" path, close Opera and delete the "Sessions" folder in the profile folder to see if it helps. That will wipe out all your tabs though.
To save your tabs, in each workspace in each window, right-click on a tab, goto "save" and choose "all tabs to a speed dial folder". Then, after you delete your "Sessions" folders, you can right-click those speed dial folders in the corresponding workspace and window and chose "open all in tabs" to get your tabs back. This method doesn't save tab islands though.
You can start Opera in safe mode and reset your flags and or disable Early Bird at the URL opera://settings/early_bird to see if it helps.