Do not lose saved games anymore
If you do not want to lose saved games just uncheck the last box when you reinitialize safari (delete all web data or in french "supprimer les données de sites web") and you will be ok. It worked for me. Since Flash is a plugin, if you delete everything on Safari you erase the flash memory too….and flash based games.
The games is quite fun when you do not lose what you achieved previously.
JanBref about Machinarium, v1.2.0