Quote: "Could be a fog problem. There is a bug in fog with some shaders."
No shader problem, thanks for you answer
Quote: "I suspect mipmapping is the culprit here. Try using set object filter ObjID, 0 on the problematic object(s)."
Changing the filter flag to zero have no effect but thank you for your answer
Quote: "I may be wrong but, have you tried changing the transparency mode?"
No but this simple idea solve my problem

Thank you
Edit: Ok I just find out a better looking solution. If I change the texture with
Set object texture ObjID, Texturing Mode, Mipmap Flag
System: Win 8.1 64 / Core i5 (3,9GHz), GeForce 760 GTX 192 - Bit Dx 11 (Driver 335.23) / 8GB Ram