There is a pretty big bug that some players get when playing the console version of The Sims 3 – it appears to occur when trying to save your gamedata (see the video below).  The only solution to this a reboot of the console, and any save data that you may of had becomes lost.  On the official EA forums, EA claims that they are aware and are looking into this issue.  Other than that, EA has no details on what triggers the bug or how to prevent it.

If you are one of the people effected, you can rant and complain in this thread.

Source of news:  Joystiq