So you are trying to upload using a link to an avatar here on a vbulletin site? That will not work. If you look at the link to my avatar here, it looks like:
http://www.vbulletin.org/custompics/...tar65230_1.gif *however* it's... um.... not exactly a gif. I know that sounds weird, and it is, but I think it has to do with the way the images/avatars and permissions work around here. I think. I'm really not sure, but I do know you will have problems. Try saving the avatar to your harddrive and then upload it (although, if I recall, that won't work either).
edit: I just saved it from here and tried to upload it and it didn't work. However, I think went and changed the .gif extension to .jpg and it did work. I'm gonna have to just scratch my head on this one. Someone might have some reason for it being this way, but I don't know it.