I can't reproduce this...if nothing else helps, i need a test case. I did this and it works fine:
Object3D test2=new Object3D(10);
test2.addTriangle(new SimpleVector(0,0,0), new SimpleVector(1,0,0), new SimpleVector(0,1,0));
test2.addTriangle(new SimpleVector(0,1,0), new SimpleVector(-1,0,0), new SimpleVector(0,-1,0));
test2.setCulling(false);
TextureInfo ti2=new TextureInfo(TextureManager.getInstance().getTextureID("grassy"));
ti2.add(TextureManager.getInstance().getTextureID("leaves"), TextureInfo.MODE_BLEND);
ti2.add(TextureManager.getInstance().getTextureID("rock"), TextureInfo.MODE_REPLACE);
test2.setTexture(ti2);