Have you cheecked your account settings, because they would have been changed to 127.0.0.1 on the server tab of your account properties and the username would also have see some subtle changes. If not the Mail Protection is not setup correctly.
Before going any further, you say you connect via a Juno dial-up, what type of email account do you use POP3 or web based, http mail?
I know that juno provide web mail but do they have regular pop3 mail? The reason I ask is avast doesn't provide support for web based email since it uses a different protocol. Any email you did download from a web based email server would be covered by the Standard Shield and not the Internet Mail provider.
I suggest you read the Setting up mail protection in the avast help file, windows start>programs>avast>help.
HTH David