Meshes that work in rex 0.31 can't be uploaded with rex 0.4.
Attached is a simple mesh produced using the technique described in http://peterquirk.wordpress.com/2008/07/15/taking-sketchup-models-into-realxtend/. The object is a cuboid with a texture on the front face.
The mesh file produced by rexmeshtool
The mesh.xml file used to create the .mesh file
The material file
Texture for material file. (reduced quality due to upload size limits)
Fixed in SVN. Related to tangent generation in Ogre.