Anybody have an idea what could be wrong?
Assuming this is only on the LCD screen (it is in this case, I can see part of the viewfinder in the top of the photo), then it may be image burn from using the screen to display shooting settings. You could try taking an underexposed photo in manual mode, eg with the lens cap on, and see if you see it on the screen. Does it stay in the same place if you zoom in on the image on the camera screen? If it does stay in the same place, then it's likely to be image burn This sort of thing was far more common on old CRT type televisions. Also check to make sure that it isn't in the image when you export it to your PC.