Ever loaded an avatar and it won't show up? The most likely culprit is that your image was just too darn large. Try resizing the picture down to 400X400 pixels or less and see if it works. If you do not know how to resize a photos, there are a ton of FREE places online that will do it for you, like this one: http://www.shrinkpictures.com/
If that doesn't do it, your connection may be getting interrupted, which would be a problem with your service provider. You'll need to contact them for help.