What patch level does your game seem to have reached? If you are at 1.67 already then the patch has probably worked. Are you able to play at all? If you seem to be patched up to date and are able to play the game, I'd be tempted to just ignore the mesage. Switching off automatic updates in the Updates tab of the Launcher should stop the messages popping up.
It is an odd error - a few other people have had it as well in recent times. If you end up needing to reinstall the game, make sure you follow the instructions for a clean uninstall. When you uninstall TS3 games on your Mac using the uninstaller, the game leaves behind stray files and isn't completely removed from your computer. These files may conflict with future installations. It is best to completely remove them. BluebellFlora's website provides a guide on how to do this:
http://bluebellflora.com/the-sims-3-on-a-mac/how-to-do-a-clean-uninstall-and-reinstall-on-a-mac/
After cleanly uninstalling, install the base game and patch it up to date. If you cannot update via the Launcher, download and apply the latest cumulative manual patch (called the superpatch) for Mac.
Check that your game works properly. Then install any EPs and SPs that you own, in order of release date.
Caspin
