***Solution***
Hi Everyone,
I wanted to respond to this post because a few short hours prior, I was freaking out about my game, Sims 3 - Island Paradise (mac), freezing while I was building a brand new house. For some reason, I was unable to return to live mode after being in build/buy mode for a couple of hours. I searched the internet and found nothing so here's what I did.
I decided to take screen shots of the house so I could rebuild it quickly after exiting the game, however, that was not needed. On the build/buy screen mode, I simple clicked the Edit town button on the left side. The options were to cancel or to continue without saving. Just continue without saving. Once you get in the Edit town screen, then save your game. It never occurred to me that you won't lose changes because you are still playing the game. Now, if you are building/buying and your computer shuts down without saving the game first- then you're probably s.o.l. -Sim outta Luck. But in this case, you are still playing the game and when you save through edit town, you save everything that you did prior to the save. Also, I do have a ton of installed content - I did not need to delete any of it!
Voila!
I hope it helps someone out there and in the words of the Sims - sousou!