Exact same problem here, Running on OS X on a MacBook Pro, repaired permissions, rebooted, checked the application folder permissions settings and they all check out. However, Checking the package contents shows that the installer is using a classic application that isn't supported on the Intel based Macs, called Update Vectorworks.. When the system asks for an admin password to give it priveledges to install it actually shows the icon used for applications that wont run on Intel Macs due to being classic apps also.
