If TRANSLUCENT is combined with SHOW, it is not working (Il will be really black because entity alpha will not work); try this instead :

ENTITY *fading_ent =
{
type = "fader.mdl";
layer = 10;
alpha = 0;
pan = 90;
flags = TRANSLUCENT;
flags2 = SHOW;
view = camera;
x = 250; // 250 quants ahead of the view
y = 0;
z = 0;
}

But I really think that the problem is with the A7 version (the SHOW flag).