SmilesTheHobbit Does this happen in a new save too? Please test for comparison's sake, with human (not occult) sims in one of the base game worlds.
If the new save crashes, please provide a dxdiag. Click Windows key-R, enter dxdiag in the run box, wait for the scan to finish, click "Save all information," and save the file to your desktop. From there, you can attach it to a reply using the paper clip (Attachment) icon included with the other formatting buttons.
If the new save is fine, try moving your main household in your existing save to a new lot in a different world, just as a test. You can also try playing different sims in the same save.