Q: iWorks '09 won't work on OSX 10.8.5, even after the update.

Recently, I updated my MBP to OSX 10.8.5, Mountain Lion, and none of the iWorks '09 applications will open, e.g. Keynote, Numbers, Pages.  I used a an iWorks '09 version that I had on my iMac, OSX 10.6.8, Snow Leopard.  After migrating the software from my iMac onto the MBP, I ran the update right away.  It is now updated to 4.3, the latest version.  However, I am getting the same error I got before running the iWorks update.  The error reads as follows:

Keynote (or any of the other iWorks applications) cannot be opened because of a problem.  Check with the developer to make sure (Keynote) works with the version of OS X.  You may need to reinstall the application.  Be sure to install any available updates from the application and OSX.  Click Report to see more detailed information and send a report to Apple.

I have tried uninstalling and reinstalling iWorks '09 several times, but to no avail.  I have also read other Apple forum postings about the subject, but none of them seem very clear on how to fix the problem.  Is there anyone, who could help me with this?

Thank you in advance!