I've found that some tiffs still have a strange error when you try to reload them via the material editor. In the preview, they are mostly black with scratchy looking lines across the top. A workaround for this is to load an alpha plane, load the offending tiff into the color channel, which will usually work, and the alpha info will be read in. Click ok, and then in the material browser, you can drag the material over onto your XFrog material. After that, just delete alpha plane. I've reported this to e-on as well, with screenshots and a tiff that causes this problem, and they're working to figure out the problem.

Sgiathalaich