I'm not sure what could be causing this. There is the small possibility your save data was damaged. Be sure to run as admin if you aren't.
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==> Find out where the game is saving:
I don't use the steam version but save data should be in your "documents" folder on windows. Steam usually makes a "My Games" folder in the documents folder.
If It's not there, then see if Bully made its own folder. The game also can make its own save data folder in the "documents" section with the game title for the folder name.
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==> Try starting new save files:
First thing I would do is wipe or at least move the save data files once you found them. If a totally fresh game allows you to save, then the save data was damaged. If saving still fails, then you will at least know it's something else.
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==> If all fails, try a reinstall or steam error check:
You could try a total reinstall or have steam run a check on the installation for errors.
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INFO:
~ If you use Windows 10, it has high security and will require you to run as admin.
~ Windows 10 has a tendency to crash with bully due to bugs. Patches had to be made so it would function. Bully was made roughly around the time of windows xp.
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