I think this happens if you install an older version on top of the newer version, without uninstalling the newer version first -- particularly if you generated a database with the newer version, on the PC or DMS, or both.
You might get it working by deleting any .db files in the PMM data directory, and maybe also phatman.ini from the main directory.
Otherwise, just completely uninstall the program, make sure the directory is gone, and reinstall the older version.