Assimp texture normals strange behaviour transparency problem

Hi together,

i have some problems with the assimp model loader and my textures and transparency. I am exporting my models from Blender to *.x files. Which works much better then the collada export from blender. I am now stuck with a problem when i use textures with alpha transparency.
There seems to be a problem with correct normal interpretation or something different. For a better understanding see a screenshot below:

The area which schould be transparent cuts away the leave behind it in the size of the actual mesh.
Now I like to know if somebody here has similar Problems and maybe a way to solve this. I am not sure where the actual problem is. Blender export is kinda crappy sometimes.

Additionaly, maybe you can tell me what is your favorite import format for assimp and what your favorite exporter?

The best format is openCollada’s dae.

which programm do you use to export dae?

I tested assimp importers on 3ds Max exporters.

i dont have max. but i will try maya export. i also tried to load obj files, but all the files loaded without texture. the obj file the texture and the mtl file are in the same folder and the path in the mtl file is pointing to the right file. any ideas on this?