I apologize by the problems. It seems Forest 4 is not adding the Presets path, if exists a previous installacion of Forest 3.
The preset's textures are stored here: C:\Program Files (x86)\Itoo Software\Forest Pack Pro\maps\Presets. There are two way to fix it:
a) Adding the path to Customize->Configure User Paths->External files.
b) Removing all Forest paths from "External Files" and restarting Max. The next time Forest is loaded, it will add all folders to the configuration.
For the render nodes, if you can't run Max interactively on them, the texture paths are defined in the following ini file (see [BitmapDirs] section):
C:\Documents and Settings\<username>\Local Settings\Application Data\Autodesk\3dsmax\<max version>\enu\3dsmax.ini
This process is valid not only for Forest, but for any texture path required by Max. We will fix the configuration procedure for the next patch.