CS5 Masking

[Michael27036180aecr]

I am working with Adobe Master Collection CS5 version, and I have been working with this version since December 17, 2010 I work mostly with Photoshop, and the trouble I am having is within Photoshop.

I am having trouble with masking. I have been masking successfully up until now, and cannot figure out what is wrong.

1. I open up an image depicting that image in the image window.
2. I click on the add layer mask button on the bottom of the layer palette to mask the image in the image window.
3. A white layer mask thumbnail pops up, and the image in the image window is still visible in the image window. It is not complexly covered by white, as it is when I invert the mask.
4. As I brush with black on the white mask the brush is displayed on the image in the image window, as well as in the mask thumbnail. 
5. I try to invert the layer mask to black by clicking on the white layer mask thumbnail, hold down the control key, and then press the i key.
6. When I invert the white mask to black the image in the image window is completely hidden with a checker board pattern, and is no longer displayed in the image window. I can paint over the image with white and what I paint reveals the image in the image window; however, this make it extremely difficult to reveal what I want revealed because the image is complete cover. I use to be able to see my image in the image window as I painted white, and the white areas I painted would be displayed on the black mask.
7. Lastly, it does not matter the color  (white, or black) of the mask, but I cannot use any of the adjustments to the mask, located on the menu bar: Image, Adjustment: Levels, Curves, Hue/Saturation, …. I use to be able to make adjustment to the areas that were masked without it affecting other areas of the image.

I understand that I am to use the white brush with the black mask to expose, and the black brush on a white mask to hide, so that is not the issue. I did something wrong, and I cannot figure out what that is, so I can reverse it. I need to know how to reverse what I caused. Any help would be greatly appreciated.