What's up with my textures?

Strange. I’m working on a simple engine and with non-textured polys ( using different vertex colors ) I get nice smoothing between colors ( prolly 24 bit color ). But when I upload a texture and render that on top of the smooth shader polygon using GL_ONE/GL_ONE I get really nasty banding effects in the clouds, like the texture is somehow being rendered in 16-bit color. The especially weird part is that it only happens on my TNT, not my Voodoo3 and my TNT2. And of course, it only happens on my TNT in my app, not any other.

What gives???

yeah, I had a similar problem but never figured it out.
If anyone knows how to fix this, I’d love to know as well.