Thank you for your response. The information you included with your image is the "Camera Data", info from Photoshop CS5.
As you may, or may not know, EXIF is short for Exchangeable Image File. This file is included, sort of, with each image you shoot.
Nikon ViewNX2 software was included with your purchase of your D3100. (If not, you can get a free download from the Nikon web site.)
In that software, with each image, you can view the EXIF information. Here is a screenshot of that information that we need to help you:
View attachment 23307
You can see the EXIF information on the right side of the screen. (There is more below what you see...) As you can tell, it reports everything about your camera settings when you took that picture. From that information, one can see what was going on with your camera at the time you captured the image. (It is listed under "Metadata") We will need all of the information listed. If you can, two screen shots of the Metadata (EXIF) would be great. First screenshot, top half of info, second screenshot, bottom half of info.
The Camera Data and the info from Nikon ViewNX2 are similar, however ViewNX2 does have a little more info that would be of use. Specifically, it will report in-camera settings that might have produced the effect you see on the "strange photos", that the Photoshop camera data will not.
When we receive this information, and the photo it pertains to (one of your "strange photos", I am sure a more knowledgeable person will try to assist you.
Thanks, and continue to have a good time on the forum...