problem with 2013-001 security update: hangs forever

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Have you tried to download and install this update from the Apple site? > http://support.apple.com/kb/DL1642

Try downloading from here

http://support.apple.com/kb/DL1642

As I told you, first download and install the update from the Apple page. Sometimes, the version you get from Software Update comes damaged or incomplete

Hey just go to this page

http://support.apple.com/kb/DL1642

and download from there

Has your problem now resolved ?

Please remember

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Try starting in safe mode. When you start in safe mode, your Mac does different things. See > http://support.apple.com/kb/ht1564

To start in safe mode, hold the Shift key while your Mac is starting until you see the Apple logo with a progress bar below. After starting, type your password and try installing that update again

Try this

http://support.apple.com/kb/TS2383

then re download

also check disk

Use Disk Utility

If the issue persists, use Disk Utility to check your Mac OS X volume. You can verify a disk while started from it. If repairs are needed, start from your Mac OS X install disc and use Disk Utility to repair.

If installation stops during "optimization"

If the installation stops during "optimization," all of the software was installed. There is no risk of an "incomplete installation." The optimization phase of an installation only affects performance and not stability or features. You may force optimization to be repeated by reinstalling the software. If you were using the Software Update pane of System Preferences on the first attempt, you will need to download the standalone installer of the same software from Apple Downloads in order to reinstall the software.

Its worth a try to locate those files mentioned in 10.5 and delete them

also read this

http://support.apple.com/kb/HT4718