You need to package off the cleanest machine possible... a simple OS with no virus scanner, no Office, etc loaded.
This ensures the snapshot will capture everything.
I also think it is good practice to also launch the application PRIOR to the "after" snapshot to really be sure you have captured everything.
Unless the software involves hardware drivers of some sort, it is pretty rare for it to fail on a different machine.
Now, different builds of machine images (ie. Finance Build, Developers Build, Marketing Build) etc. that can cause issues..hence the need for the cleanest machine possible....