We have to different packages that were created by Apple Professional services, knowing that we use Casper. We tested all packages with ARD at time of creation and just added them to Casper. These are being deployed to 10.8.4 computers that are at the login window and I know at least one of them runs a script as it is a universal bind script they wrote for use that displays what it is doing in big text across the screen.
Anyone else have a problem with .pkg in Mountain lion via Casper.
I have had this happen several times with different packages. In every case it has come down to permissions problems with items inside of a non-flat package. Just like you for some strange reason installing via ARD is never a problem, but Casper fails to install. IIRC in most cases I changed the permissions of the affected file in the package to 755 and Casper would then install it correctly.