yeah something with the map file went wrong, maybe you tried to alter it and it saved the alpha channel differently.
View attachment 539697
also some small observations: I think most objects are too bright, you use 0.5 or 0.6 for ksDiffuse and ksAmbient which may be a bit high. Your crowd in the grandstand may look and work better if you used the normal Kunos camera facing crowd mechanic (using the camera_facing.ini), which you could also use your existing texture for if you don't want the standard Kunos rendered weirdos
But its a great track and a great recreation of this classic as it is