Dave,
Did you get this message with the regular installation package from "Check for Updates"? If so, maybe you can try the off-line package.
Follow this link:
http://www.objectiflune.com/OL/en-CA/Download/Software/PlanetPressSuite.aspxAnd download the off-line package. Uninstall your current version, then run the 7.5.2 offline installer. It should include all the packages you need. (and don't worry about uninstalling, the update uninstalls the previous version and install the new one, so it's the same procedure)
If you are still getting errors even after that, then you will have to contact Technical Support and have them investigate this with you. You may call 1-866-348-5863, or use the web page:
http://www.objectiflune.com/OL/en-CA/Support/ReportIssue/PlanetPressSuite.aspxRegards,
Raphaël Lalonde Lefebvre