Here are some tips to try:
1. Deactivate Origin In-Game
Open Origin, Go up to the Origin Menu, Click Origin and select Application Settings. Select the Origin In-Game tab. Make sure the box for it is clear or unchecked or turned Off. - This deactivates Origin In-Game, as it has been known to cause problems with games.
[Origin in-game is a feature that allows you to see friends online in-game as well as other game stats. However, It has been known to cause problems having this feature turned on.]2. Repair Game
Go to My Games Library - Right-click on Sims 3 and Select Repair.
3. Try a factory reset of game
Sims 3 Factory Reset (What & Howto)
http://www.carls-sims-4-guide.com/forum/index.php?topic=20732.msg401814#msg4018144. Uninstall/Reinstall the game
Uninstall the game via Origin or the Control Panel
- Origin -- Go to Games Library and right-click on Sims 3, select Uninstall. This will uninstall all of Sims 3 and it's packs.
- Control Panel -- Control Panel > Uninstall a Program > Find Sims 3 and it's packs and uninstall each of them.
Install Sims 3 and expansions via Origin
1. Log into your Origin Account with the email and password you used to purchased the game with.
2. Click on the Game Library tab, right-click on the Sims 3 and select Download. This will download the base game and any expansions, and stuff packs that have been purchased. The download process includes any bonus items.
** There should be no need for the game code, as Origin already has that information. However, if you have this problem, please read the link below for more information.
This Code Has Already been Used
http://www.carls-sims-4-guide.com/forum/index.php?topic=21899.msg431138#msg431138It is recommended to run Ccleaner and it's registry cleaner Or a similar registry cleaner, after or before installing the game again. To help clean up files that get left behind in the registry after an uninstall.
Ccleaner, It's free
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http://www.piriform.com/ccleaner/download -- PC
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https://www.piriform.com/ccleaner/download?mac -- Mac
How to use CCleaner to fix PC issues
http://www.wikihow.com/Use-CCleanerWith Medieval not launching either it maybe best to uninstall/reinstall it as well. An alternative is to register the game with Origin for a download copy.
The download version has an advantage of the launcher being removed and you can repair game if needed.
Also with Origin games you can download them, back them up and restore them. So you don't have to re-download the entire game if you need to reinstall.
How-To: Backup and Restore The Sims 4 and 3 From Origin
http://www.carls-sims-4-guide.com/forum/index.php?topic=21193.msg384770#msg384770