1. The new avatar has the same name as the old one so the computer doesn't download the new image..
The computer uses the old image from memory because it doesn't know the actual image has changed, the great majority of the time this saves on bandwidth where you are constantly downloading the same image (like an avatar).
Reboot your computer or flush your temporary internet files and it should show up properly.
You should be able to browse from your desktop or any folder where you have a picture saved to use, and:
Avatar images will be resized to 48x48 pixels. The maximum file size for avatar images is 10kb.
USAGE POLICY: We expect members who upload avatars to adhere to the community standards for this message board. Anyone who uses this feature as a means to disrupt the message board may risk losing their avatar upload privileges. If your avatar is judged to be disruptive, it will be deleted. The administrators have final authority over what is considered disruptive.
Use any picture you have or have saved, select the image, then hit "upload"