Anyone had this happen? So heartbroken

I think my poor D300 has taken a poop... Started giving me this overexposed, linear area on every photo. Ive switched lens and memory cards and no help... Here is what is happening. Any suggestions?

Wondering if that's not a problem with a shutter getting snagged a little as it travels.
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That doesn't look good! I'm wondering if there's a sensor problem, or as Fish said, a shutter problem. How many actuations on that camera? Perhaps it's time to send it in to get looked at by a Nikon tech. The camera is definitely worth keeping, IMHO, but then again, I'm a diehard D300 fanatic!

Had the camera been sitting idle for a long time before that shot was taken?
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Um, I've used this camera extensively... I've got over 136000 actuation's on this one. Its ALWAYS on me. The previous photos have a black area on them. Then the overexposed area. Here is the photo just before this happened.

time to send off for service or possibly upgrade or find a gently used D300 on the market.
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That's definitely shutter. Take a long exposure to make 200% sure. Else, either time to upgrade or replace the shutter.

How long since you've had a real tuneup? I mean a good cleaning? Might just be some dirt or something getting into the shutter mechanism. Just a guess.

I say shutter, could be very expensive fix, I would upgrade to more a current camera better to spend $ on new camera, but that's me..........

Open a ticket so Nikon can take a look at one of your jpegs. They might be able to give you an idea of the problem as well as quote you a ballpark amount for a repair. It won't cost you anything to upload a photo for them to take a look.

Yep, that's the death throes of a shutter