Tombstones are not the culprit. The thing which usually crashes lots on load is cellphones. Make sure no sims are using a cellphone when you save your lot, or it will crash on load. If this happens, you'll have to crowbar it, depending on your usual pattern of cellphone behavior. The most likely thing that will cause a cellphone to be out on a save is the AutoYak: To resolve the lockup, remove it from your hacks, load your game, and the offending sim should reset as his phonecall object is yanked out from under him. Then save, quit, put it back.
If you were using the "Call Sim" functionality, you'll need to use the
cellphonerst package to crowbar your phone. It functions similarly by breaking the call object, forcing a reset, and enabling the lot to finish loading.