I don't know what you used to change the save file and what all the field(s) you edited. However - messing with save files may have adverse effects. Since you have edited the save file and you are having problems - it raises a red flag.
Also, a suggestion - never save on top of a previous save while you still have empty save slots available. Since the game automatically opens the save file window every morning, each day can be a new save slot (day 1, slot 1 -- day 2, slot 2 -- etc). There are, what, 50 save slots (more than in-game days, currently). And if something fouls up, one of the previous saves may be helpful.
That said, I used a save editor to add funds, myself - but I haven't experienced any problems with gameplay.