This exact symptom showed up on my old D60 when I gave it to my daughter and after a week of use it got dropped. Very short distance - it was inside her backpack and the backpack fell off a chair.
What it was is the shutter curtain came out of it's guide and won't slide up all the way. The shutter curtain is a flexible piece of metal. I sent it to the Nikon repair HQ after filling out the form. The repair cost $200 plus shipping. They repaired it by replacing the shutter curtain. Now since you can get a used D60 for just a little bit more from B&H you have to decided if you want to get it fixed. (She did only because it has sentimental value - it was my camera which I passed on to her.)
Start here to get repair information.
Yau-Man