It looks like this is another problem related to the model optimisation. There is one palm tree in desert4 now that you cannot select.
In tileset desert4 you have a tree called palm2_1.g3d . This model conains two seperate Meshes. One Mesh is used for the little bushes around the palm and the other one is the palm itself. Meshes have options in g3d and I used them to make the bushes non selectable ( you can see this in G3dHack very good ).
But now some kind of model optimasation must do something that the palm too is no longer selectable. The flag "non selectabel" means that the Mesh is not rendered when in selection Mode. This is a feature I took over from GAE some time ago ( its already in 3.7.2 )
So meshes with different flags cannot be merged into one mesh...