Disable slight window transparency in OS 10.4?

[Morgan19]

I'm running 10.4.11 and've just run into a problem with a slight bit of transparency my windows have. It seems to be happening in Firefox (version 2.0), so I'm not sure if it's an OS thing or a Firefox thing.

My browser window appears to have a slight bit of transparency, like it's at 95% opacity. If I take a screenshot of a website and in Photoshop try and sample a few pixels of color from what I know to be an area of solid color, I'll get four or five versions of the color sampled– it's happening because the screenshot is grabbing not only the displayed webpage but also the little bit of window or background showing through behind it.

Has anyone had this experience with being able to slightly see through a Firefox window like this? It's a tiny thing, but it's throwing my workflow off enough that I need to be able to fix it.

(EDIT-) Looks like it's not just Firefox, I'm getting some window transparency see-through in Photoshop as well.

Thanks,
m19