I could see three of them stuck in the middle -- like they went to open up to a wider aperture and couldn't.

It's possible it's a connection thing. I've had problems with this lens since day one...it often doesn't connect with the body, and I get "F--" where the aperture reading should be displayed. A bit of twisting fixes it, but it's needed more of that lately.

I sort of wonder if I've had a bum lens from the beginning. Of course, I have it home. (Don't keep the D50 or the expensive equipment at school here in NYC with me --- just have a D40 that I use for shooting in the city, and get the other stuff from home for big events.)

It's very possible that the connections are the issue. As I said, it's been getting worse.