Nikon D90: Shooting on Manual produces all black photos?

A few nights ago I was doing a photo project in the dark and was messing with my settings. Ever since, when I take a photo on Manual the photo shows up completely dark like it didn't let any light in. I tried to change all of the settings that affect the light, and I reset the settings completely back to the cameras standards. Still, it is producing photos that are black no matter what. I don't know what to do or what I did and I would really appreciate any insight.

Where's your aperture set? And your shutter speed? Does the camera produce photos in full auto and in the program mode? If so it's not the camera, it's you.

So check again. Set it like this. Shutter at 1/200, aperture at f/5.6. Go outside and shoot and see what happens.

Now, don't mis understand, it could be something wrong internally but that's not very likely with a good quality camera but, if it is, then call Nikon.

Sounds like you have the ISO/Aperture/Shutter Speed setting wrong.

When you put the camera into manual, you are supposed to make the proper adjustments in these three settings for a proper exposure.

That is the purpose of manual - to allow the photographer 100% control over the exposure. Which means, you can incorrectly set the ISO/Aperture/Shutter Speed.

Is the lens cap on?
J/K

Okay if the lens cap is off, put the camera in full AUTO mode.
Set WB to AUTO
Set ISO to 200
Take a few photos and see it the camera takes photos okay.
If it works that way then look at the information the camera used for the settings.

Switch to A priority and adjust the aperture to what the AUTO setting was for it.
Take a few shots, should look alright and take note to what the shutter speed was at.

Now switch to S priority and put in what the camera was using for shutter speed.
Take a few shots, should look alright and take note to what the aperture setting was at.

Now switch to M Priority and set your aperture and speed to the auto settings results.
Take a few shots, should look alright.

I recommend after using the camera for any specific type of shots, you do a full reset of the camera to ensure your custom settings for that shoot don"t interfere with setting up for a new one. JMO