Much appreciated, raynonn!
I'm actually trying to find some cause/solution for this problem. I might have found a problem with the camera, and it could be that the aperture lever is not working properly. It will fire without the lens, but, when I put my AF-D lens on, (I tried two of them) it gets stuck. So, I put my modified Helios on, and it appears to be working.
So, technically, it's not totally dead yet. I have to ask around about this aperture lever problem. Now, I have a manual lens platform in my D90!