Problem with Updates

I am suddenly having a problem installing Mac software updates...whenever a restart is needed the system hangs on configuring installation and will not go any further, same with updates not requiring restart.....any input would be much appreciated.
The latest updates affected are OS 10.5.6 and Quick time....

Download the combo updater and Quicktime 7.6.1 from the Apple wen site. After download is complegte, drag to desktop, disconnect peripherals other than keyboard and mouse, disable antivirus if connected and run Repair Permissions.

Double click update and let the machine reboot. Sometimes there will be two, or more, sets of chimes, and up to five or six minutes rebooting time. Just be patient.

When all updating is complete, again run Repair Permissions, and hook up peripherals etc.

Mac OS X 10.5.6 Combo Update

Download Apple Mac OS 7.6.1 update 7.6.1 Free