Delete Old Files
One cause for receiving an error when you start the Sims 3 Launcher is the presence of old files that were left in your Sims file folder after a game update. To fix this problem, close Sims 3 and open a Windows Explorer Window. Open your computer's Documents folder and then navigate to the Electronic Arts subfolder. Then open "The Sims 3" folder and delete the Version.tag file that is contained therein. Next time you start The Sims 3, the game will reproduce an accurate version of this file. If deleting the Version.tag file doesn't fix your problem, the next step is to reinstall your game update software.
Uninstall Origin Downloader
Origin is the name of the Electronic Arts download manager that serves the Sims 3 and other EA applications. If your version of Origin is corrupt, then any game updates that you receive may also be corrupt and cause the Launcher to malfunction. To uninstall Origin, hold the Windows logo key and press the "R" key to open a command box. Type "appwiz.cpl" in the box and press Enter to open the Windows Programs and Features control panel. Then right-click "Origin" in the programs list and click "Uninstall" in the menu to uninstall the Origin downloader application. Once the program is uninstalled, reboot your computer.
Reinstall Origin Downloader
You can download a fresh version of the Origin downloader from the EA Origin website at origin.com/eadm. Entering that Web address into a browser will automatically initiate a file download. Double-click the downloaded file and follow the on-screen instructions to install a new copy of the Origin downloader to your computer. Once the Origin downloader installation is complete you can use it to update your Sims 3 program and launcher application.
Update Sims 3
To update The Sims 3 manually, run the Origin downloader application and type in the email address and password that you used to register your copy of the Sims 3. You will proceed to a screen that shows an icon for The Sims 3 and any other EA games you have recently played. Click The Sims 3 icon and then click "update" to update your copy of the Sims 3 to the latest version. Then run the Sims 3 Launcher and follow the on-screen instructions to download any additional Launcher updates that are available from EA.
Tech Support
If you are still having trouble with The Sims 3 Launcher then EA suggests that you create a thread on the official Sims 3 technical support forum. You can access the forum by typing "forum.thesims3.com/jforum/forums/show/10.page" in your Web browser. Then create a new forum thread by clicking the "New Topic" button located under the "Forum Index" heading.