Sims 3 won't update. "Invalid file found."

I have been trying to download a new update for my Sims 3 game. But, every time I near the end of the update, a box pops up that says "Update Error: Invalid file found" and this other box says "The wizard was interrupted before the Sims 3 could be completely patched. To patch this program at a later time, please run the patch again." Does anyone know how to fix this without uninstalling and reinstalling my game? And if I do uninstall and reinstall it, will by games be deleted?