My D300 started acting quirky several months ago and then died last week. The problem was not old batteries. It started with the shutter not working. Then, the auto focus would not work. After turning off and on, it worked again. Then it didn't....
Another odd thing: I got a "grey" screen when I looked through the viewfinder on several occasions. Thinking the problem was a bad battery connection, I gently pushed the battery tighter in the compartment. This caused the grey screen again. Minutes later, I heard a ffffsssst, and everything quit. The mirror permanently locked up. No life, no matter what I did.
Called Nikon, and they had me push two reset buttons at once. Nothing. I had been using a Promaster 8 gb memory card for the past two years. Nikon said it was not an approved card and could have caused the problem. Nobody I know has ever experienced such an issue.
I plan to send it in for inspection and possible repair. Meanwhile, I'm using my old D200. Now that is starting the same quirky behavior. I wondered if the problem could be with my much older 300mm f2.8 AF-I lens or the Kenko Telepro Plus 1.4 teleconverter. Nikon said its teleconverters won't work with the older lenses because new electronics don't match the old. But yesterday I saw somebody shooting with a D300 and exact same older lens with a Nikon 2X teleconverter, and it was working fine.
Anyone care to speculate on what might be causing these issues? I'm expecting a used D700 to arrive soon, and I definitely do not want to corrupt that by using suspicious accessories.