Glitches

Glitches (or bugs) are errors in a game or program that cause unexpected problems or unwanted behavior.

Causes
Glitches in The Sims series of games can be caused by any of the following:
 * Use of some cheats (notoriously Testingcheatsenabled).
 * Installation of official game updates/patches.
 * Use of game modifications.
 * Use of downloaded objects.
 * Hardware problems: A malfunctioning computer component or a computer that does not meet minimum game requirements.

Many glitches are so minor that they can be ignored, even if they occur often. Some glitches, while they do not corrupt any game data, may make the game partially or completely unplayable. Examples of these include graphical errors that cause the game to not render or display correctly. The most severe glitches may corrupt saved game data or cause a CTD (Crash To Desktop). Severe glitches also include Save game errors; bugs that can prevent a game from being saved.

The best thing you can do is contact EA about your problems with glitches. You can find lots of contact info for them in your game manual. Their site already contains ALOT of helpful information in their Possible Bugs forum.

Confirmed Sims 3 Glitches
If you want to add a glitch please go to the talk page and see if someone already reported it. If multiple people are experiencing the same bug it can be added to the list. If you can reference a website which reports this glitch, that would be best.
 * Save game error - (Error 12, Error 13, and Error 16), which prevents games from saving in The Sims 3. This was introduced in World Adventures. Patch 7 was released to fix this problem and Patch 8 introduced a recovery prompt for already corrupted games.
 * Unable to open Consignment shop buy menu - The game is supposed to return items to you which haven't been sold within 5 days, but it does not work. Instead the items start counting down into the minusses, preventing you from opening the buy menu. This can be fixed by cancelling your consignments.