Re: Sims 2 Ultimate collection: Black rectangle shadows

Solution 1 - lower or turn off your in-game shadow settings. Some people report that setting shadows to Medium is fine, some have to turn them off altogether so your mileage may vary. You can do this once you have loaded a household.

Solution 2 - there is a mod by MTS user Nopke that also takes care of this issue. Not sure if I can link to mods in here but I'm sure you can find it based on the information given.