I hate to be the one to have to tell you this, but from what you said, it sure sounds like your save is corrupt. Depending on how many times you've saved, you might be able to recover an earlier version from before the crashing started. If you have saved more than 5 times since it started, you'll be out of luck but if you've saved less, you should be able to recover, at least enough to save most of the lots and sims to your Library. If you have saved more than 5 times and all the save versions have the crashing problem, then hopefully you have a backup somewhere that you can use to either play on or recover from.
To try a recovery, use the Main Menu Load option and open the Load Menu. Just to the left of the Play and Delete buttons, you will find the Recover Save button. Just press that and it will open a panel listing all the recovery choices. I suggest you pick the last one as that will be the oldest. But you can try with any listed there. Then follow the prompts. Once done, open the recovered save and see if that works. If not, then repeat until you've gone through all the choices. Hopefully one will work for you but as I said earlier, if you go through all the choices and none work then hopefully, you've got a backup somewhere.
Hope this helps.
