So in the middle of taking a set of pictures, I noticed that my D90 was not actually saving the pictures I took. The mirror would flip up, the shutter would click, but the display would show the same older picture again.
I tried the usual suspects. Turning the camera off and on. Changing the directory on the card where files were supposed to save. Swapping out memory cards. Reformatting memory cards. Doing the two-button reset. Doing the menu reset. Pulling out and then replacing the battery.
I could shoot a picture with a blank memory card installed, and the display would say “Folder contains no images.”
I searched on the internet for this symptom, and found no other reports of it.
Here’s what finally cured it:
* switch into LiveView mode
* take a picture – this will fail
* take another picture – this will succeed
* switch out of LiveView mode
Et voila! Now it works. I don’t know if this is reproducible, nor if I’m just heading down a path toward permanent issues, but I figured it would be worth posting just in case anyone else has the same issue.