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Please, download the attached file and run it (double click). It will delete the required registry entries.
Forest includes a mechanism to add the texture paths automatically to Max, for the library items.
It scans all library paths, searching for a 'maps' folder, and adding them to the registry (HKEY_CURRENT_USER\SOFTWARE\Itoo Software\Forest Pack Pro\TexturePaths). Later, these entries are added to Customize->Configure Project Paths->External Files.
If libraries are removed, it may be necessary to clean this registry to delete old entries.