I think it's to do with the new patch, 1.63, as I've started getting it too. Does it look something like this?
http://bluebellflora.files.wordpress.com/2013/11/screen-shot-2013-10-27-at-14-22-29.png
I just hit ignore and the game loads fine and saves fine. I think you've automatically selected to send info to Apple when you set up Mavericks. Try disabling it and see how your game runs:
System Preferences > Security & Privacy > Privacy
Then scroll down to Diagnostics and Usage and untick the box next to "Send diagnostic & usage data to Apple".
Next time it comes up just click on Ignore.