How to override faulty Cubase 5 Mac OS Detector?

Cubase 5 will not install on my Mac mini. It claims I am not running the required OS version. However, I am. It wants 10.5. I am running 10.5 (upgraded from 10.4). Every time I run the installer it says I am not running 10.5.

I suspect that the Mac OS upgrade DVD did not overwrite all system records. Perhaps it did not update the system record that Cubase 5 is checking.

When I go to About This Mac, it correctly identifies my version as 10.5

How do you override this Cubase OS version checker?

Solution found! At least, it seems to work so far. Control-Click on Cubase 5.mpkg, do Show Package Contents, drill down a bit, install the Syncrosoft Package, then install Cubase 5.pkg.