If it looks OK in other applications, but not in CS2, it's likely to be a colour management problem (yet again!). The chances are that it's an sRGB image that CS2 thinks is Adobe RGB, perhaps because the colourspace isn't tagged in the JPG file. AFAIK even though it's a mono image the colourspace still matters, but I may be completely wrong here.
If that ain't it, all I can suggest is using Paint Shop Pro.
