Sims 3 - There was an error during startup.

[Braxton]

Whenever I open Sims 3. the only thing I get is this:



This has never happened before. What could the problem be? I do have Master Controller and the cheats module, could this be the problem?

Note that after I click OK, it just closes.

[MrsFlynn]

I searched on this problem and found what's happening is something glitched in the registry or there's entries left behind from installing/uninstalling programs. You can use Ccleaner and it's registry cleaner to clear that up.

Ccleaner, It's free
- http://www.piriform.com/ccleaner/download  -- PC
- https://www.piriform.com/ccleaner/download?mac -- Mac

How to use CCleaner to fix PC issues
http://www.wikihow.com/Use-CCleaner

I've used Ccleaner for years and works really well for cleaning up registry issues. Or you can use Regedit and edit the registry yourself. 

1. Click on the Start bar or type Start and type in Regedit.
2. When the program opens, click the arrow of the HKEY_LOCAL_MACHINE
3. Click the arrow of the name Software.
4. Scroll down until you find the name WOW6432Node and click the arrow of it.
5. Scroll down and click the arrow of the name: Sims
-- From there you may see some expansion packs.
6. Delete the expansions you don't have, by right-clicking on them and select Delete.

The issue is with the registry glitch, not Nraas's MasterController.

[Braxton]

I have the Steam version. Does this change anything for Regedit?

[MrsFlynn]

That I don't know, as I haven't used Regedit. I clean my registry using Ccleaner. You may need to ask on the Sims 3 - Steam forum to see if they might be able to help answer that question, if you haven't already.

[Braxton]

Apparently, my backup folder of my Sims 3 saves(I recently deleted my old saves) contained an Appaloosa Plains save from Sims 3 Pets, which I uninstalled. I deleted the Appaloosa Plains folder, and launched the game. It worked perfectly.  I didn't even screw around with the registry. It was a file for an xpac I uninstalled.

[MrsFlynn]

I'm happy to hear you were able to fix it. Yay!!