My D5300 is only taking black pictures suddenly

My Nikon D5300 is suddenly only taking black pictures. It sounds and acts like it is taking pictures, but nothing shows up on the preview screen except a black picture, and when I look at the images on the PC, they are all black as well.

I have tried all the usual things, like replacing with a fresh battery pack, reformatting the Memory card, I have reset the camera using the <Menu> and <i> button.

I can see the shutter opening and closing while taking a picture.

I can go into live view, and even record a video. This does play properly on the camera itself, as well as the PC.

I can NOT take a picture, either in live view or normal mode.

I have adjusted the ISO settings, and have tried different modes, like sport, etc.

This happened practiaclly from one moment to the next. I took pictures, turned off the camera, turned on the camera, and it only took black pictures.

Very intrestingly, pictures (on my PC, after downloading from sim card) rotate Horizontally or vertically, depending on how I took them.

Also, image sizes vary from picture to picture however not in the normal range: instead of 5-7 MB, now only 1-2.5 MB,

Lastly, I went ahead and updated the firmware to now 1.03 from 1.0 . No change.

Any ideas would be greatly apprecaited!