Mac OS X 10.5.6
Mac OS X 10.5.6 combo update
Mac OS X 10.6.7 Update is recommended for all users running Mac OS X Snow Leopard.
It includes general operating system fixes that enhance the stability, compatibility, and security of your Mac. In particular, it includes fixes that:
Improve the reliability of Back to My Mac
Resolve an issue when transferring files to certain SMB servers
Address various minor Mac App Store bugs
Mac OS X 10.6.7 is an essential update for Snow Leopard users.