I presume you mean the error occurs at the LW installation process and not the Security installer step?
Does it actually install? I do not have OSX 10.8 (still 10.6) so I am not sure if the original LW installer has any issue with OSX 10.8.
Post-Flight would normally refer to the very last step of installation (probably after the app itself has been installed.) This may refer to a user profile or Java path linking. If Java is not installed then a problem would occur.

I do know OSX 10.8 is not packaged with Java. You will first need to install Java for OSX 10.7 or later before installing LW.

Let us know how things go.