I have an image looking just right, but can't flatten it without severe changes

[Alp...@adobeforums.com]

I'm having a problem with Photoshop CS3 10.0.1. Here's what I did:

1. I created an image - 6x4 inches, 600 dpi.
2. Created a new layer, and filled it with black.
3. I ran the Add Noise filter - 15%, Gaussian, Monochromatic.
4. I added a Curves Adjustment Layer. I set the dark end point to 0/49 (Out/In), and added another point at 98/60 (Out/In).

This now looks the way I want it to. However, if I try to merge the Curves layer with the noise layer, the end result changes drastically. The same thing happens if I try to Flatten Visible, Flatten All, or create a Layer Stamp. It even happens when I apply the Curves directly, instead of as an adjustment layer.

If I try to work with the original background layer without creating a new layer first, it seems to work fine when I merge the Curves layer with it. But if I duplicate the layer, I get the same problem.

I can't get this to change into a single layer without changing. What the heck is going on?

[J_Ma...@adobeforums.com]

View at 100% to see an accurate preview of noise fields and their adjusting layers.