Re: Endless Saving
@keelyfern It sounds like there are two main possibilities here. First is that your game is borked. The presence of NRaas mods makes this less likely, but still possible. Hopefully, you have ErrorTrap, Overwatch, and MasterController already in place; if not, now's a good time to add them. You might try a MasterController reset of the entire town as soon as you load up your game—click on City Hall, NRaas > MC > Town Options > Reset Everything. It might take a few minutes to complete, but if you watch in Map View, you should be able to see sims being reset back home as the command runs.
If this doesn't help, you can try all of the above on the backup copy of your save. Even if you never make backups yourself, the game keeps a copy of the file from the second-to-last time you saved. Hopefully, this isn't corrupted too, or at least is less so. In your Saves folder, you can find that save, remove the .backup extension and rename it, and then it will appear as an option at the Main Menu like your other saves.
The other possibility is that your save is using almost all of the RAM available to it just on startup, and even a few minutes of gameplay pushes it over the edge. That would explain why you can save right at the beginning of a play session but not later on. You can check RAM use in the Task Manager—put the game in windowed mode, open TM, and watch what happens as you try to save. If you're seeing percentages of memory use, right-click on the category heading to switch to absolute numbers. TS3 is a 32-bit application and can therefore use only 4 GB RAM at a time, but the danger zone is anything above 3.7 GB. If your save is consistently near this limit, then you'll probably need to pack up your active family and move them somewhere else.
If none of this helps, please run a dxdiag and attach the results here (use the Browse button). Please also list the packs you have installed, the world you're playing in, and which mods you're using.
https://answers.ea.com/t5/The-Sims-3/HOW-TO-DxDiag-PC-Only/m-p/1049584/thread-id/47181