Do not turn off your virus protection…
Avast does not corrupt the dbx files.
I suggest you backup your OE files (dbx, Windows Registry, Rules for messages and so on). Use: Outlook Express Freebie Backup 2.9.0.3 (http://www.oehelp.com/OEBackup/oebackupfiles2.9.zip), it’s a freeware! 8)