Sims 3 Wont Launch

Try the following steps from crinrict's great FAQ:

Problem

When starting the launcher, I get the error message: There was an error during startup. See the Log for more details

Cause

The most common reason for this issue are left over registery keys from uninstalling the base game or any of the EPs. Run CCleaner (only registery cleaner and do backup your registery) to remove those and if it still doesn't work, do a manual search either for Sims 3 or by going through the list of keys here: http://simswiki.info/wiki.php?title=Game_Help:TS3_Uninstall

If this doesn't help, try the suggestions below.

Suggestions

• Reinstall Origin
• Solution by Georgia82 for digital downloads (be aware that the patch linked is not the newest. Use the patch here: http://answers.ea.com/t5/The-Sims-3/FAQ-Patch-1-67/td-p/67858/)
• Make sure your graphic drivers are up-to-date
• Bypass the Launcher and start your game directly
• Right click on the launcher icon and start your launcher as administrator
• Make sure your Microsoft .net Framework is current
• Put in the base game DVD or start the game from the base game launcher icon instead of the addon
• If you uninstalled an EP make sure there are no left-over keys in your Registry. For information on Registry Keys, check this guide: Manually Uninstalling The Sims 3
• Uninstall CAW and CAP and try to start the launcher. If that works, redownload the tools and reinstall them after cleaning your registry with CCleaner.
• If you manually moved the game or part of it (don't do that), the references in the Windows Registry are messed up. Reinstall your game.
• If you installed your game on an external drive, there might be a problem with the drive letter. Make sure that your drive has a fixed drive letter.
• Remove your User Files

This error often occurs after patching, so make sure you always backup your user files in documents\electronicarts\thesims3 before patching.

Let us know if this helps. 🙂