Well I created a terrain and got a wierd message, you have no terrain on your scene but it was plainly visable anyways removed it and regenerated the terrain and it worked..
Made some hills and auto painted it... worked great
Placed some grass worked great.
Went to put some rocks so in the drop down changed it from trees to rocks and it crashed...
I have no idea why its crashing.
I have uploaded a DX Diag so you can see my system spec's..