Alpha transparencies on interiors... doesn't work?

Hi, I have some problem in getting an interior with alpha transparencies to work...

At the beginning it was working but when looking at trees behind it the foliage doesn't show...

Then after various temptatives now I always get a full transparencies of the material (it no consider the alpha layer... ) and what is very strange is that I'm no more able to change the texture file name given by the baseTex[0] parameter... The texture file had the same name of the material but now if I try to change the everytime I try to change the baseTex[0] parameter to something else I get the NOMATERIAL texture showing in game...

How is this possible?

Any idea?

Here is the material definition I'm using (I don't know nomore how many temptatives I've done...)

new Material(_CANIONS_FADE)
{
baseTex[0] = "_CANIONS_FADE";
translucent = true;
translucentBlendOp = LerpAlpha;
// translucentZWrite = true;
alphaTest = true; // default value would be true
alphaRef = 20; // anything below this number is not visible and is not written to zbuffer
// emissive[0] = true;
};

Tnx,
JoZ