Sim family that won't save to the library

@BillFlowerpot  The hidden object interactive loading screens are shown while your save is loading.  You try to find the listed object and click on it, thereby earning lifetime happiness points for the sims you're about to play.  This option is on by default, but you can turn it off easily enough.

I could have sworn I mentioned it before, but I guess I didn't:  One other approach, if you haven't already tried it, is to switch active families, quit, clear caches, reload, then try to save this household to the bin.  (Evict first if you need to, or try the other suggestions that didn't work before, especially including the clean game folder.)

A couple of final suggestions on saving this family:  First, empty out their personal and family inventories completely, then quit, clear your cache files, reload, evict, and save from there.  It's possible one of the inventories contains a corrupt item.

The other thing you can try is splitting the family in Edit Town and saving them separately.  I understand it's not exactly what you're looking for, but at the very least, you'll find out if one of your sims is corrupt in some way.

Mods are game modifications, written to add features to a game and/or clean up errors.  If you're not already interested, I'm not trying to sell you on them.  But if you are, this is a good tutorial:

http://modthesims.info/wiki.php?title=Game_Help:Installing_Sims_3_Package_Files/Setup_and_Files

The mods I use to keep my game clean are all from NRaas.  I can recommend a few, but first, make sure this is something you're comfortable doing.  Not everyone is, which is fine, but there aren't really any more in-game ways I can think of to force the family to save.