I know I fixed this in the past on my setup - I think I copied the shadow texture from the first version (not TS2012 updated) of the hopper and it worked ok. I dont have any of the files anymore...so I cant verify. But it is fixable.
If you download this car made by Larry Goss: http://www.trainsim.com/vbts/tslib.php? ... &fid=24614 and you copy the 'softshadow' from this car into the folder of the SP hopper, you should be on the road/rails in no time.