My game on my Mac laptop does the freezing for a few seconds thing too when I switch between Sims or Map view. I think basically it's an issue of the laptop having just enough processing power (no idea what the Computer speak word is) to run the game. My advice would be to lower your graphics (in game under Options) and the High Detail Lots number. My game has most things turned to low except if they bug me. For example, I have my Texture and Sim Details at the highest settings. I make sure to always pause the game before switching between Sims and in/out of Map view. My game still does the freezing thing but it's not as bad as it used to be. Also, I don't have anything running in the background when I'm playing TS3, not even the internet. Everything is off (except Finder, of course).