One of my websites logo's had this same problem, a strange white coating around most things in the image. What i did was, if you have photoshop, I took the gif and opened it back up, then used the Select Colour Range tool to highlight all the white and delete it, then when I saved the gif again and re-imported it (in my case, back into dreamweaver and the WWW), the white was gone and the image looked as it should.