I've had another thought, fortheloveofcake. And if this is a duh one, I apologize, but I figured I'd ask. Does it happen only in games that you've been playing through for awhile? AKA how legacy challenges are going? Also, have you tried looking at a computer monitoring software that allows you to see how hot your core is getting? It could possibly be a heat/fan issue, especially if it's after you've had the computer running processes all day, etc.
Either of those two things are culprits for me. I fixed my cooling issue by pulling my tower out from under my desk, and when it's hot out I run a fan over it and me.
I'm not trying to drag out a solution, but I'd like to help you find a non-mod answer, too.
If there's anything at all that you notice going on at the same time or whatever, even if it's something like listening to youtube in the background, let me know and I'll start digging. I've got quite a little list of all these weird lag issues I had with sims when I first started, so I've got (probably too) many help resources for the issue.
And there's nothing more frustrating than just wanting to let your sims run so you can relax and play, only to have the game itself bugger up.