Hi, these errors are caused by a missing masxscript used for the "Quad" menu, both in Forest and RailClone.
Specifically the maxscript files are: <max folder>\scripts\Startup\forestpack.ms
It would happen in two cases:
1) If the plugin is installed, but for some reason the script is missing or was not exectuted at Max startup.
2) When the plugin is uninstalled, Max keeps a copy of the macroscript used in the Quad menu, even if the plugin was removed correctly.
In this case, you can fix it deleting the macroscript copies, as described here