September 2020
No mater what I try, I just can't prevent this error. I've tried deleting cache, moving The Sims 3 folder from documents out, uninstalling and reinstalling, and deleting Origin cache.
September 2020
@sonic1236788 One cause of the "serious error" message is having the Sims 3 folder open while you try to load a save, so please make sure you close it before launching the game. Just to be clear, have you moved the entire Sims 3 folder out of Documents\Electronic Arts and let the game generate a new one, then launched it without adding any content to that folder? It's important to test with zero content in a new folder, just to be thorough.
If doing the above doesn't or didn't help, please run a dxdiag and attach it to a post.
https://help.ea.com/en-us/help/pc/how-to-gather-dxdiag-information/