That happens randomly and is probably a memory leak in the game engine. So the best advice is to save regularly. If you started from the beginning or used a provided bookmark then after playing an episode a bookmark will automatically made. See my walkthrough (link to latest version in signature) for the exact moment this is done. You can use those through the options menu. So at most you loose the progress from one episode...Make sure you save before going in the basement after Giovanna, Giulio caught me and I got sent to the hospital, when I came too and talked to the nurse, the game got stuck and I could not do anything.