Thank You for the file, suppenhuhn. In our tests it seems like scene is slow, ForestPack has nothing to do with it.
Opening this scene (not very large) takes more than 5 minutes. Even longer time is needed to open Material Editor.
Easy fix for this scene- merge all it's contents to new, empty, 3ds max scene. After doing that there is no problem creating FP items.
Hope this helps.
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