We've isolated the problem and we're working on its solution. This issue is related to the "automatic clean-up process" of duplicated objects used by the Forest Pack plug-in stored in the "forest_templates" layer.
Until it'll be fixed, to avoid this kind of problems, please move in any of these scenes such object(s) under another layer - to not have duplicated names in the "forest_templates" layer which is checked during saving the scene. You can find all these imported objects under the "forest_templates" layer. By default, all objects inside of this layer are hidden and frozen. The object name will be _forest_library_*******. Any of these objects can be manipulated like any other 3ds Max's object - moved to another layer etc.
Hope that helps.