That's a bug
Here's some tips: http://forum.thesims3.com/jforum/posts/list/655767.page
or check out this post: http://answers.ea.com/t5/The-Sims-3/FAQ-Savegame-Corruption/td-p/968290/
Recently, I've seen some cases have the same issue. Some of them starts a new game at the custom world. When they sent a sim to University from EA world, they didn't have a problem. Some of them are using laptops has under 4 GBs of memory. This may cause some error while travelling to WA world or Univ world from lack of Rams I think. 🙂
