Component changed when moving from one .skp file to another?

[IntelCoreDuo]

I've modeled a tree with components within components. Then I used this tree to create a second, different tree where I alter the geometry and replace the textures.

However, when I move both trees into the same file then one of them gets the textures from the other. It seems like some of the components have the same ID tag somehow and get replaced. If I explode every component the issue goes away, but not if I simply rename them. Any solution to this?

[IntelCoreDuo]

Just to explain more clearly:
I made an aspen tree with aspen "leaf" level 3 components grouped together inside a level 2 "branch" component grouped together inside a level 1 "tree" component.

Then I used the aspen tree component to make a birch tree in a new file. I replaced the Aspen leaf .tif texture with birch leaf .tif, and changed the branch shapes a bit.

Then I make a new landscape file and insert the birch tree. Later I insert the aspen tree. However the Aspen leaf.tif texture is now replaced with the birch leaf .tif texture. It seems SketchUp remembers that the leaf level 3 component was the same.
Changing the components and sub-component name before importing makes no difference. The only thing that helps is exploding the leaf component.

This would be a nice solution, except the tree is much more complex than explained above, with tons of different level 3 leaf components, which are not easy to find. Also I modeled a handful of trees before discovering this problem. So, either a solution to the issue of help figuring out the logic behind this problem would be greatly appreciated.