I too have this problem, it happened after trying to patch up to 3.6.6. Unfortunately I patched by downloading it from the web and running the exe instead of using the launcher. Guess I'll be spending tonight un & reinstalling
Edit: After several uninstalls and reinstalls I've finally got a solution that worked for me. I'm posting it as a suggestion for anyone else with this problem.
1 Uninstall all Stuff Packs, Expansion Packs and the Base game (including things bought from EA Store, saves games etc. Don't forget to backup your saves!)
2 Clean up PC (optional)
3 Reinstall Base game ONLY and use Launcher to update to latest patch (1.15 at time of writing)
4 Repeat step 3 for World Adventures (patch 2.10) then High End Loft (3.6), Ambitions (4.2?), Fast Lane and if it's out Nightlife. Remember to use Launcher to update each one before installing and updating the next.
5 Reinstall Store items and copy your saves back into save folder.
You should now have a working game