@rasmaldus What happens if you switch to a different household while playing, evict the original household and place them in a different house, then quit to desktop and reload before trying to save them? Be sure to delete the five cache files in Documents\Electronic Arts\The Sims 3 before you start and after you quit to desktop in between steps. For reference, the files are:
- CASPartCache.package
- compositorCache.package
- scriptCache.package
- simCompositorCache.package
- socialCache.package
Another thing that sometimes helps is emptying out all the inventories of the affected sims, at least as much as possible. A few items can't be removed, but most of it should be removable.
If that doesn't help, try splitting the household and only saving one half. You probably want to save them all together, but if you can save one half and not the other, you can try splitting the other half again until you find out which sim is affected. (It's still a good idea to quit to desktop, delete the cache files, and reload after saving fails.) If you can save both halves, then maybe the issue is the cumulative size of the household in terms of all the data being saved.