Image Adjustments won't stay on

Question

     Hey everybody, I'm Steven! I'm working on a sci-fi mural spacescape for my art class, and I'm having a bit of difficulty in the star scape area. See, whenever I do anything in the "Image > Adjustments" tab at the top of Photoshop, the preview on my page makes it look just how I want it, but after I click OK, or Apply, it either goes right back to how it was before I did the adjustment, or it does it to a degree, it just goes back halfway.
For instance, when I click "add noise", then go to Image > Adjustments > Levels to thin the noise out to resemble stars, as a base layer to my starscape, and get it perfect, with the right amount of contrast and everything, when I click OK, it just goes back to big ugly noise. Now, I've added adjustment layers, but those effect everything under them, and I kind of need this to be specific. I've tried changing my mode to 32, 16 and 8 bit, as well as from RGB to CYMK and others. If anyone could help me out, I'd be really grateful! Thanks!
(P.S. I'm using CS4, if that helps)
Steven.

Answer 1

   Well, I did have one file that looked similar to it in the directory I was opening it from, so to be safe, I moved it and tried again, but it didn't work. The thing is, when I do Image > Adjustments, the preview on my actual canvas looks good, but when I click OK to lock it in, it just goes back to the way it was before, or kinda how I wanted it, but only a fraction, like half power. And when I save it, it also won't stay on. It will keep effect if I add an adjustments layer, and give me the desired effect, but it affects all the layers below it, not just the one I want, and it will revert to what it was before the effect if I save it as anything but a .PSD, for instance a .PNG, it will go back to white noise, not stars, just like Image > Adjustments. I did both Save and Save As, but they both had the same outcome. Haha, it seems I've really gotten myself in a pickle. Thanks for helping me out -
-Steven