Cannot open Mail or Safari after having updated to 10.6.8

Question

I have a Macbook (late 2008 silver version). I formatted my drive and re-installed OS X Snow Leopard 10.6.3 from the installation disc (Mail version was 4.2). I then downloaded and installed the MAC OS X Update Combo 10.6.8 (Mail version became 4.6). Since then, my Mail and Safari app will not open and both give me this error message:  Mail cannot be opened because of a problem. Check with the developer to make sure Mail works with this version of Mac OS X. You may need to re-install the application. Be sure to install any available updates for the application and Mac OS X.
I have downloaded all OS X updates (from the Software Update command)...but the problem still persists. Can anyone HELP?

Answer 1

Try a restart.
Do a backup, using either Time Machine or a cloning program, to ensure files/data can be recovered. Two backups are better than one.
Try setting up another admin user account to see if the same problem continues. If Back-to-My Mac is selected in System Preferences, the Guest account will not work. The intent is to see if it is specific to one account or a system wide problem. This account can be deleted later.
Isolating an issue by using another user account
If the problem is still there, try booting into the Safe Mode using your normal account.  Disconnect all peripherals except those needed for the test. Shut down the computer and then power it back up after waiting 10 seconds. Immediately after hearing the startup chime, hold down the shift key and continue to hold it until the gray Apple icon and a progress bar appear. The boot up is significantly slower than normal. This will reset some caches, forces a directory check, and disables all startup and login items, among other things. When you reboot normally, the initial reboot may be slower than normal. If the system operates normally, there may be 3rd party applications which are causing a problem. Try deleting/disabling the third party applications after a restart by using the application un-installer. For each disable/delete, you will need to restart if you don't do them all at once.
Safe Mode