Lightmap Baking suddenly stops

I've done it countless times before without an issue now all of a sudden it starts and i can see the progress bar for about 30secs then it just stops during the "Building ADS Structure" phase. I get an error that says

"UV set on Mesh is incorrect. Lightmapper needs UVs inside the (0,1)x(0,1) space. UnityEditor.DockArea:OnGUI()"

and it highlights one of my trees meshes(my main one i am using for my scene with the tree tool) when i select the error. How do i fix the problem?