Game Crashing after 5 minutes of gameplay (real time) - screen frozen, clock stopped, sims frozen...

LOL, you aren't supposed to get emotionally attached to test games but I've let that happen myself.

Okay, this is good we've ruled out just about everything else. So you can either keep the new game folder or, what I would really suggest, set it aside, put the original back in, but remove the most recently added content and clear caches. Since this only just started happening, seems like the most likely candidates would be content that either was never there before or was never being used until now.