When a new avatar is approved it replaces the existing one on our servers immediately.
If your Avatar aspect ratio changed, then some old threads in some forums may squash or stretch your new avatar.
Never fear, it'll sort itself out. We recommend only uploading square avatars for this reason.
If your browser contains the old cached copy it may show, and not always consistently. Your local browser cache may need to be updated for your new avatar to appear. Simply refresh or reload any page that has your avatar on it, and the new one should appear. If not, if your ISP has a proxy server there is still a chance the image is archived further upstream but out of our control.