iLife ’09 checksum changes on every instadmg run

hello all, i'm working on building and testing my first image built with instadmg, and the ilife '09 checksum is changing on me with each instadmg run. if I use the new checksum, everything goes smoothly, but it's a little strange since none of the other packages i'm adding are showing this behavior. Any ideas? thanks!! edit: one thing i should probably mention- the machine i'm running instadmg on has it's HD encrypted using PGP. Should I avoid using PGP-ed machines when building images using instadmg/instaup2date?