If you updated Safari to version 5.1 and then applied the OS X 10.6.8 v1.1 update, you will need to redownload the latest version of Safari again.
Toast 4.0.2 updaters are out
A number of people have mentioned not being able to update to OS X 10.6.5, especially when they have used the standalone Combo updaters that have been found at sites like MacUpdate. After installing these updates, they have found the system still to be running OS X 10.6.4.
When you run the Software Updater in OS X, the system will present the latest updates for your system. While this is handy for most people, many times people will not want to update to the latest version for compatibility reasons, and instead may wish
Firmware updaters may persistently give "Up to Date" messages at bootup.
Mac OS X 10.3: Combo updaters; positives; troubleshooting
Retrospect updaters posted; fix Mac OS 9 conflict
Mac OS X 10.1.2 standalone updaters; Open Firmware Password instructions
The standard fixes prevail again.
If your system refuses to install the latest OS X update, there are several steps you can try to get it working.