Assuming you followed the Photoshop instructions for a rotating avatar to the letter (the ones that require Adobe Imageready). The first thing that comes to mind is that you may have saved the image at too high a filesize, or the image dimensions are not within limits. In either case the forum software will take only one image and resize that image automatically to fit within the forum's boundaries.
If you would like me to take a look at it, feel free to email your avatar to me
