You can take a look at the log file in the ldclient map on a client where you deployed this package. There should be a log file with a name identitical to the MSI that logs all actions taken by the installer.
Are you running the distribution with any switches to make it a silent install? If so what are your results when running the same switches from a command line? I have seen a few vendor MSI's where the UI level has adversely affected the install.
Just an FYI...
I discovered and our TAM was able to replicate this, when using an MSI package and a "Public" Delivery method to push and have it cache locally, that LANDesk for some reason is ignoring the cache locally and running the package from the Source.
This is in LD8
Only happens if the Push delivery method is a "Public" one and it is using UNC
Private (My Delivery Methods) and HTTP seem to work