Are you using the ground blend texture from Goldrush?
I had this too once awhile back but can't remember how I fixed it.
But what you can try, and this is to make sure it's not a video card thing, copy a chunk of displacement from Goldrush that has the grass and paste into your map. Do a bsp compile only and see if that new displacement section shows any grass sprites. If it does, well, you did something wrong to your original displacement. I would look at the displacement settings for the Goldrush chunk and make sure yours is the same. If it still doesn't work, but the Goldrush chunk does. Just delete yours and resize the Goldrush chunk to what you want.
My current project I am using Blendgroundtograss003 and I can see my sprites for as far as the displacement goes.