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

Thank you a lot :) !

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

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 .

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: .