It's a known issue.
Here's some tips: http://forum.thesims3.com/jforum/posts/list/655771.page or check out this post: http://answers.ea.com/t5/The-Sims-3/FAQ-Savegame-Corruption/td-p/968290/
Graduation is especially glitched. Do you have a backup ?
No I dont have a back up. Ironically I saved after she had graduated as when she left the annex things were a bit busy and I couldn't interact with anyone, so I saved the game. At the time I wasnt aware of this glitch otherwise I would have taken a different route to stop my game corrupting.
Is there anything else I can do apart from install mods?
Thank you
I think there's some suggestions on that forum (not AnswerHQ) link. I don't know if they will work though. With the corruption you describe, I don't think much can be done without resorting to mods
I just really hope they fix this in the upcoming island paradise patch.
I don't think it will resolve any current corruptions but not getting new ones would be a huge step.
