I am using outlook express and windows XP (SP2).
With Windows 2k\XP, avast 4.6 has a new mail detection that will work automatically. Please, set up your email account just as avast does not
exists. It will detect the pop3/smpt/imap ports and scan your messages. Can you make a try and see if it's ok? New email detection is automatic and do not require user interaction. Anyway, spam killer applications need manually change email account settings
If that does not work, can you try to repair your installation?
Go to Control Panel > Add/Remove programs > avast! antivirus > Remove
Then choose Repair function in the popup window (Repair).
You must be connected to the internet while repairing.
If this does not help, can you uninstall / boot / install / boot again?