Install error when removing old version

So we have some systems running an old version of PDFCreator v1.2.3. We’re trying to get these updated to the new version. I run the newest installer v2.2.1 and it begins the removal of the old version, then errors with:

Runtime Error (at 295:207):

Internal error: An attempt was made to expand the “app” constant before it was initialized.

At this point the process closes. The old version is removed successfully, but the instal does not continue and needs to be run again. Since I need to do more machines than i’d like by hand I wanted to make an INF to help automate the process. So far the installation just hangs if I do it silently, and this is the problem i discovered when doing it manually. 

Thanks in advance for any help. Installing the 64-bit version to Win7 64.