I have a problem with the shutter on my D90?

I just tried to take a photo with my Nikon D90 and, when I clicked the shutter release, the shutter closed but did not reopen all the way. On the top-display, it showed "err" in the shutter speed space. Once I clicked the release button again, the shutter popped back open. However, there was no photo taken. This problem continues. Sometimes, nothing at all happens when I click the shutter release button.
There are only about 46, 600 actuations on my shutter so, I'd be surprised if it's failing this early, as they are rated for 100, 000.

Added (1). Begging your pardon. I wasn't thinking about that clearly. Long day. Looking back now, I think it is the mirror. The problem is that the viewfinder remains black so, it sounds like it's staying up. However, no file is written to the card. That may be unrelated, though. As all mine were full, I borrowed a card from my mother's camera, so it's formatted differently.

If can be failing already. Try to take the camera outside, set Auto mode, AF on, white balance to Auto, ISO to Auto, and EV to 0 then shoot a brightly colored car parked under the sun from about 10 feet. If that does not come out consistently good (take a number of shots) then something is terribly wrong with your camera. That 100, 000 rating is only a guide. Most do not reach that number.

You have your terms backwards… The shutter doesn't close to take the picture it opens. If it sticks open then your photos will be white because they're over exposed. If it sticks open for a time and the view finder is black that's because the mirror has raised out of the way to allow light to get to the shutter and then to the sensor.

46-thousand is quite a bit. It could be ready for a tuneup from Nikon. Get in touch with them and try to explain the problem properly so they'll understand you.

Attached the camera with PC, run the software cd, reset the settng and reset the auto option.