I can't repro anything like that with 2.5 and 2.74. Can you provide a blend?

Not really, partly since I still use Blender 2.72b as of yet, partly since I don't have any sessions with that bug saved. Edit: But try enabling auto-smooth, mark something as sharp, then disable auto-smooth. In Blender, the disabling should work properly, but as far as I'm concerned, the Blender Source Tools still load those sharp edges (in 2.4.1 at least).

I've got the same bug, and it litterally broke the model by the way. I can provide screenshots and blends file if you want c: .

Screen here : http://img15.hostingpics.net/pics/203905Screenshot3.png
Left : After exported to DMX. (nothing change if i select "Import SMD Polygons & normals")
Right : Before export. I didn't ticked the "auto-smooth" option nor custom split normal data, it added itsef at the export. If i untick it, the model return like the model at the right (before export) But each time i export it tick it.
Also clicking the auto-smooth tickbox doesn't brick anything on the original model.

Blend file :
http://1drv.ms/1QsBKiD
Experienced with Blender Source Tools 2.6.1 & Blender 2.74, 75 & 76 .

There's nothing wrong with my export of the mesh. Can you send me the original blend please?

Okey ! http://1drv.ms/1G6fFWV original, so with materials names & shapes flexes in Japanese. I personally usually rename them before exporting, or it give me a warning message
Aaalso i use the SFM's DMX exporter. Zappy too i guess, i often see him on SFM's community

I'm getting the problem now. I'll look into it!

Thank you a lot :) !

I've poked at this problem for a while this weekend and I think your mesh may have some sort of messed up internal state. The exporter does some work to mesh objects before exporting them, and it relies on Blender not altering vertex or loop order during that process. That appears to be exactly what is happening.

The good news is that if I export the mesh to FBX then reimport it the DMX is generated correctly. I've also been able to alter which areas of the exported DMX get bad normals/UVs by running the Separate op.

In short, you should look into refreshing the underlying mesh data in a way which doesn't alter its appearance. The FBX re-import looked fine to me. :)

Try going to Edit Mode with the mesh that breaks when exporting, select all vertices, and press Shading > Smooth Vertices (or such) in the left panel, then export again. If I remember right, that fixed it for me last time I had this problem.

Additionally, try enabling "Auto Smooth" on the mesh. I found that doing that would also make the same error show up in Blender.

Okay ! I'll remember about FBX export & import
But does it keep materials, armature and everything ?
EDIT : Yep it does, thanks !