Problem with mirror Nikon D300

[^Demon]

Hello

I wanted to ask members of forum for advice.

I have Nikon D300 and for a last month I had a problem with mirror.

When you taking a shot it makes a very loud sound and it feels like mirror sticks, and in result I got black picture.

Did anybody had any similar problems?

I bought this camera from Jacobsdigital and it still on a warranty.. but the problem is that I need this camera very bad and cant give it away for more than 2 weeks.

Regards

[Flash In The Pan]

Have you tried taking the lens off and watching to see if the mirror is lifting when you take a shot?

[^Demon]

The problem is that happens once in ~400 shots. But it looks like it happens more often that it was before