Sounds like a bug with your avatar not registering the change. Try this.
- Go to "UserCP"
- Select "Edit Your Avatar"
- You should see your avatar, and beside that an option that says "Do not use an avatar." Select that option then scroll down and click the Save Changes button.
- Make sure it has removed the avatar from the database, then attempt to upload your new avatar via the "Browse" option. Upload by URL does not work due to a vB error.
By selecting "Do not use an avatar" first, you are erasing all existence of your account having an avatar selected in the database. This allows the server to easily reckognize that you are adding a new avatar and should remove any issues of the server ignoring the request.