I am in a DNP program and will finish (I Hope!) May 2011. I have had the same issues. At first I didn't realize when nurses asked, why are you doing that? , that they were being negative. I tried to explain that I wanted to learn more, etc. Now I just say Why not? That stops them.
It seems to be a variation of the nurses eat their young sort of thing. Instead of being supportive, like crabs, some people try to drag you back down into the bucket.