Sorry I canīt help. It never happened to me before.
Make sure that the textures files sizes are correct. You sould use something like 1024*1024, 512*512, 256*256 and so on. (or even 1024*512, 512*256, I donīt remmember all the options right now)
Or maybe something with the mesh, you canīt have two vertex or faces in exactly the same place. If you are using max you can run the STL check utility which is very useful for this.
It doesnīt explain why it shows up in the mod viewer and the utils, but who knows.....Maybe the game engine is somehow more sensitive....
Mariano