On both my PowerMac G5 and iMac Core Duo, both running Mac OS X 10.4.8 and VTPro 4.2.1, the main window shows nothing. I can initiate a scan by clicking on Check For Updates but the list remains blank... on both machines.

Just today, I looked up Acrobat Professional on versiontracker.com and the page indicated that it is not installed on any of my machines monitored by etc.

Not true. I have Acrobat Pro 7 on my iMac and versions 7 and 8 on my G5. VTPro is not getting any better at all.