Just an FYI - I had this happen to me as well, twice. I'll have to see if I still have the pictures, if you want them, because I actually found that it wasn't just floating on the map screen, but also in the game play as well. and it actually happened when I was messing around with the move objects on cheat right after it was released from EA. and I had not turned it off after using it. Once I got back into my game, and played it, and then saved and exited my game, everything was back to normal the next time I loaded the game. But, like the other player stated, insteaded of clicking on the house, you have to click on the land where the house *should* be in order to get the option to play your game.
I'm not sure why forgetting to turn off the MOO would cause the whole lot to move - but I feel confident thats what happened since it happened to me twice and both times thats what I had done (and knock on wood, it's never happened since!). If you'd like the pictures, I'll see if I still have the screen shots. But I just recently cleaned out my folders. Let me know! Hope this helps!