What are you trying to install?
iWork '09 ? or some other version of iWork?
What version of OS X do you have installed?
Which Mac model?
Are you within the system requirements for iWork '09?
Have you tried the iWork install while booted into safe boot mode?
If you launch that installer again, then open the installer log - there's 3 different logs: Errors, Errors and progress, and Show All Logs.
One of those logs may help you see what is causing the fault during the install process. In particular, you might look near the beginning of the Show All logs, where you may see other software, such as the system version - you would be looking for OTHER information about apps that are running.
Another possibility is to check All Processes in your Activity Monitor.
(I'm sure you know some of this already - what else have you tried?

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