It has nothing to do with "uploading". The avatar system is completely outsourced. Once you added an avatar to your e-mail, it's a problem of the provider Gravatar to do all the things. This system here just requests the avatar for a certain e-mail address from Gravatar. Maybe you should have a look at the Gravatar support center.
Btw: Where's the problem with waiting a bit until the avatar is shown? It's just a gimmick.