This happens because the Advanced Wood map is a 3D texture that is centred using an object's position and orientation to calculate the map. This makes sense when it's applied to a single object, but when you apply the map to a Forest Object it takes the entire scatter into consideration as a single object and the coordinates, therefore, don't look correct. Basically you would get the same mapping issue if you collapse Forest Pack to a single mesh.
There are a couple of things you could do to work around this limitation:
1 - Instantiate the Forest object using Forest Tools. This would convert the scatter to standard Max instances that would be compatible with this map
2 - In Forest Pack 7 you could enable Non-Geometric Object for the item in the Geometry rollout. This is a bit of a hack that will use a different instancing technique designed for lights and other non-geometric items. It should render fine, butbe aware that viewport displays will be affected and you won't be able to use Forest Colour.
I hope that helps,