Snow Leopard Screenshots and Grab not working

Recently, I have upgraded from 10.5.x to to 10.6.2 and then 10.6.3 and the Screenshots (Cmd Shit 3 / Cmd Shift 4) and Grab app are not function properly. That is no images are generated.

The solution is to reinstall the
Mac OS X 10.6.2 Update (Combo)
http://support.apple.com/downloads/DL959/en_US/MacOSXUpdCombo10.6.2.dmg
or
Mac OS X 10.6.3 Update (Combo)
http://support.apple.com/downloads/DL1017/en_US/MacOSXUpdCombo10.6.3v1.1.dmg

Then these problems will be fixed.
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