I get this error when trying to use your save. Any chance the global is needed?i created a savegame with all sex-scenes for mom and sis unlocked by hardcore cheating. So whoever (like me) gave up to beat the game for real can check this out to get access to all sex scenes. You can also sleep until vacation end and then choose with who you wonna stay with for additional sex scene in the ending sequence.
Have fun
I did the whole create a save in file1 and then replace it with the save you provided "trick", but no luck...